JP5170686B2 - Measuring apparatus and measuring method using nuclear magnetic resonance method - Google Patents

Description

  The present invention relates to a measuring apparatus and a measuring method using a nuclear magnetic resonance method, and more particularly to a technique for measuring a current at a specific portion of a sample using the nuclear magnetic resonance method.

  As conventional methods for measuring the surface current distribution of a sample, there are methods described in Non-Patent Documents 1 and 2.

  Non-Patent Document 1 discloses a method of measuring the current flowing in each divided electrode by dividing the electrodes into “divided electrodes” when measuring the current distribution in the surface direction of the fuel cell, and isolating them individually. Have been described.

Non-Patent Document 2 describes a method of measuring the strength of a magnetic field using a Hall element. Here, the Hall element is an element having a characteristic that the electric resistance of the element changes in accordance with the intensity of the magnetic field applied to the element. Non-Patent Document 2 proposes a method of obtaining a current distribution by measuring a spatial map of the magnetic field strength by moving this Hall element close to a fuel cell and spatially scanning it, and analyzing it as an inverse problem. ing.
Kazuo Onda et al., “Measurement of membrane properties and current distribution analysis / measurement of polymer electrolyte fuel cells”, Proceedings of the 13th Fuel Cell Symposium, 2006, p. 234-237 Masaaki Izumi, Yuji Goto, “Research and Development on Measurement Technology and Modeling of Polymer Electrolyte Fuel Cells”, Summary of NEDO Fuel Cell / Hydrogen Technology Development Interim Report Meeting, published on December 27, 2005, p. 39-40

  However, the methods described in Non-Patent Documents 1 and 2 described above have room for improvement in the following points.

  First, in the split electrode method described in Non-Patent Document 1, it is necessary to manufacture a fuel battery cell in which a split electrode is incorporated, and the actual measurement is performed using an apparatus for measurement, which is different from an actual machine that does not use a split electrode. There is a possibility that the measurement result is obtained, and there is room for improvement in terms of the reliability of the experimental data. In addition, each time a new cell is designed and manufactured, the divided electrodes must be designed and manufactured again, which is not practical in terms of increasing development costs.

  In the method using the Hall element described in Non-Patent Document 2, the magnetic field generated by the current flowing in the electrode is measured. This magnetic field strength is almost equal to the strength of the geomagnetism and is a weak value. It is. In order to accurately measure such a weak magnetic field strength, the Hall element is required to have high resolution and high reproducibility.

  For example, if a Hall element is used to measure a fuel cell, the Hall element is sensitive to temperature changes, and is installed in and around a fuel cell that generates heat to measure the magnetic field with the Hall element. Is prepared in advance so that the nonlinearity of the element can be corrected with the relationship between the current or resistance value flowing through the Hall element measured at each temperature and the applied magnetic field strength as a calibration curve, and applied to the fuel cell. It is necessary to take a very time-consuming method of calculating the magnetic field from the calibration curve after measuring its own temperature with very high accuracy. Furthermore, there is a problem that it is difficult to measure the true Hall element temperature.

  For these reasons, the method using the Hall sensor has been studied, but it is still in the research stage and is far from practical use.

  As described above, with the conventional technique, it is difficult to locally measure the current distribution in the surface of the sample.

According to the present invention,
An apparatus for locally measuring a current at a specific portion of a sample using a nuclear magnetic resonance method,
A static magnetic field application unit that applies a static magnetic field to the sample;
A small RF coil smaller than the sample, which applies an oscillating magnetic field for excitation to the sample and acquires a nuclear magnetic resonance signal generated at a specific location of the sample;
Calculating a difference between the frequency of the nuclear magnetic resonance signal acquired by the small RF coil and the frequency of the oscillating magnetic field for excitation, and from the difference, a current calculation unit that calculates a current at the specific portion of the sample;
A measuring device is provided.

Moreover, according to the present invention,
An apparatus for acquiring a current distribution in a plane of a solid polymer electrolyte membrane of a fuel cell using a nuclear magnetic resonance method,
A static magnetic field application unit that applies a static magnetic field to the solid polymer electrolyte membrane;
Applying an oscillating magnetic field for excitation to the solid polymer electrolyte membrane and acquiring a nuclear magnetic resonance signal generated at a specific location of the solid polymer electrolyte membrane, a plurality of smaller than the solid polymer electrolyte membrane, A small RF coil;
For the plurality of small RF coils, the difference between the frequency of the nuclear magnetic resonance signal acquired by the small RF coil and the frequency of the oscillating magnetic field for excitation is calculated, and the surface of the solid polymer electrolyte membrane is calculated from the difference. A current distribution acquisition unit for acquiring the current distribution in
A measuring device is provided.

Moreover, according to the present invention,
A method for locally measuring a current at a specific portion of a sample using a nuclear magnetic resonance method,
A first step of applying an oscillating magnetic field for excitation to a specific location of the sample placed in a static magnetic field using a small RF coil smaller than the sample and acquiring a nuclear magnetic resonance signal generated at the specific location When,
Calculating the difference between the frequency of the nuclear magnetic resonance signal acquired in the first step and the frequency of the oscillating magnetic field for excitation, and from the difference, a second step of obtaining the current at the specific location of the sample;
A measurement method is provided.

  In the present invention, an excitation oscillating magnetic field is locally applied using a small RF coil smaller than the sample, and a nuclear magnetic resonance signal emitted from a location where the excitation oscillating magnetic field is applied is obtained. The current at a specific location of the sample is obtained from the magnetic resonance signal. A local current in a predetermined region of the sample can be measured in a short time by limiting the portion to be measured with a small RF coil and applying an excitation oscillating magnetic field.

  In addition, the measurement accuracy can be improved by using a nuclear magnetic resonance signal with high frequency resolution when obtaining the current. Also, by calculating the difference between the frequency of the nuclear magnetic resonance signal and the frequency of the oscillating magnetic field for excitation and obtaining the current from the difference, absolute measurement such as the measurement using the Hall element described above with reference to Non-Patent Document 2 is performed. Compared with the method using values, the influence of environmental changes around the element such as the temperature environment and the need for a calibration curve can be reduced, so that the measurement accuracy can be further improved.

Here, the difference between the frequency of the nuclear magnetic resonance signal and the frequency of the oscillating magnetic field for excitation can be specifically obtained as (ii) below with respect to (i) below.
(I) The RF oscillator has (stores) an oscillating magnetic field for excitation, which is a “reference frequency when no current is flowing”.
(Ii) “amount by which the frequency of the nuclear magnetic resonance signal is increased or decreased by the magnetic field formed by the flow of current”
The above (ii) is measured, for example, as a phase change amount.

  At this time, the frequency of the oscillating magnetic field for excitation is equal to the frequency of the nuclear magnetic resonance signal under the static magnetic field created only by the magnet when no current is flowing, and the magnetic field created by the current flowing The difference between the frequency of the nuclear magnetic resonance signal measured under both the magnetic field and the static magnetic field originally applied by the magnet. The frequency difference is measured from the phase difference.

  In the present specification, the “static magnetic field” is not a completely stable magnetic field as long as it is a temporally stable magnetic field capable of stably acquiring nuclear magnetic resonance signals and currents. There may be some variation within that range.

  In the present invention, in order to express the obtained current as a spatial distribution, it can be expressed as a current density by dividing by the area where the current flows.

The measurement apparatus of the present invention may further include a detection unit that detects a real part and an imaginary part of the nuclear magnetic resonance signal, and the current calculation unit detects the real part and the imaginary part detected by the detection part. May be used to calculate the difference between the frequency of the nuclear magnetic resonance signal and the frequency of the excitation oscillating magnetic field.
In the measurement method of the present invention, in the second step, the real part and the imaginary part of the nuclear magnetic resonance signal are detected, and the frequency of the nuclear magnetic resonance signal and the excitation are detected using the real part and the imaginary part. It is also possible to calculate a difference from the frequency of the oscillating magnetic field.
Thereby, the difference in frequency can be obtained more simply and reliably.

  In terms of the difference in frequency when the amount of phase change at a certain time interval is converted per unit time, the detected magnetic real part and imaginary part are used to determine the nuclear magnetic field when the excitation vibration magnetic field is used as a reference. The amount of phase change in a certain time interval of the resonance signal or the difference between the frequencies of the two may be calculated.

  In the present invention, each sample type includes a storage unit that stores information indicating a correlation between the difference between the frequency of the nuclear magnetic resonance signal and the frequency of the excitation oscillating magnetic field and the current, for example, calibration curve data, and the current The calculation unit may acquire the information corresponding to the sample to be measured from the storage unit and calculate a current based on the information.

  In the present invention, the sample to be measured can be a film, for example. At this time, the local current in the film can be grasped.

  The measurement apparatus of the present invention includes a plurality of the small RF coils, and the plurality of small RF coils apply the oscillating magnetic field for excitation to a plurality of locations of the sample and acquire the nuclear magnetic resonance signal. And the said current calculation part may be comprised so that the electric current in the said several places of the said sample may be calculated.

  By doing so, it is possible to simultaneously measure multiple points of current with a simple configuration. For example, if the sample is a film, information on the current distribution of the film can be obtained. Arrangement | positioning of a some small RF coil is arbitrary, and can be arrayed according to the shape etc. of a measuring object.

Here, the small RF coil applies, for example, the pulsed oscillating magnetic field, obtains an FID (Free Induction decay) signal corresponding to the oscillating magnetic field for excitation, and the current calculation unit The real part and the imaginary part of the FID signal can be acquired. At this time, it is only necessary that the magnetization vector is excited with an excitation pulse that can obtain a significant FID signal compared to noise, and the angle at which the excitation pulse excites the magnetization vector (the angle that is tilted with respect to the static magnetic field direction). Is optional.
By making this angle arbitrary, it is possible to shorten the recovery time of the magnetization vector related to the T ₁ relaxation time constant, and it is possible to irradiate the excitation pulse with a shorter repetition time and to measure the current distribution in a short time. It becomes.

Further, the small RF coil can apply an excitation oscillating magnetic field in the following sequence, for example, and can also acquire an echo signal corresponding to the excitation oscillating magnetic field.
(A) a 90 ° pulse, and
(B) A 180 ° pulse applied after elapse of time τ of the pulse in (a).

  The excitation oscillating magnetic field is a pulse sequence including the above (a) and (b), and the current calculation unit converges the phase of the echo signal by using the spin echo method of acquiring the real part and the imaginary part of the echo signal. be able to. Further, as will be described later, measurement errors due to magnetic field inhomogeneities can be effectively reduced. For this reason, the measurement accuracy of the real part and the imaginary part of the nuclear magnetic resonance signal can be further improved. For example, in the second step, the real part and the imaginary part of the echo signal are detected, and the difference between the frequency of the nuclear magnetic resonance signal and the frequency of the excitation oscillating magnetic field is calculated using the real part and the imaginary part. It may be calculated.

  In the present specification, the “FID signal” and the “echo signal” may be signals that correspond to the excitation oscillating magnetic field and function as nuclear magnetic resonance signals capable of detecting the real part and the imaginary part.

  In addition, the “pulse sequence” in the present invention is a sequence that defines a timing diagram for setting the time and interval for applying the excitation oscillating magnetic field. Here, the timing diagram also includes a procedure table for performing necessary operations in time series.

  In addition to the above pulse sequence, another sequence in which a step of applying a 180 ° pulse is added at a time τ before the 90 ° pulse (a) may be executed. By comparing the intensity of the NMR signal acquired by the 90 ° pulse (a) and the intensity of the NMR signal acquired by appropriately selecting the time τ at the 180 ° pulse (b), the vibration for excitation irradiated from the RF coil It can be judged whether the intensity of the magnetic field corresponds to 90 ° or 180 ° accurately. It is measured that the intensity of the two pulses is 1 to 2, or the irradiation energy is 1 to 4 or the pulse application time is 1 to 2, and the magnetization vector is excited to 90 ° and 180 °, respectively. It is an important factor to improve the accuracy and reproducibility. As a result, even if the relationship between the two pulses becomes inappropriate due to device abnormality or immature adjustment, the abnormality can be detected before the measurement is performed, and the measured value can be made more probable. .

  Further, in the present invention, an RF signal generation unit that generates an RF signal for generating the excitation oscillating magnetic field in the small RF coil, and an echo signal acquired by the small RF coil are detected, and the echo signal is An echo signal detection unit that is sent to a current calculation unit and a branch unit that connects the small RF coil, the RF signal generation unit, and the echo signal detection unit are connected to connect the small RF coil and the RF signal generation unit. And a switch circuit that switches between a state in which the small RF coil and the echo signal detection unit are connected to each other.

  By doing so, the loss of the high frequency pulse signal for excitation applied to the sample from the small RF coil is reduced, and as a result, the pulse angles of the 90 ° pulse and the 180 ° pulse can be accurately controlled.

The pulse sequence of the oscillating magnetic field for excitation can also be configured to include the following (a), (b), and (c).
(A) 90 ° pulse,
(B) 180 ° pulse applied after time τ of pulse (a), and (c) n 180 ° applied at intervals of time 2τ, starting from time 2τ of pulse (b). pulse.
Note that n is a natural number.

  By using the pulse sequence comprising the above (a) to (c), the current at a specific portion of the sample is measured using an echo signal corresponding to the pulse of (b) or (c), and (b) and ( The amount of protic solvent in the sample at the specific location can be measured using a plurality of echo signals corresponding to the pulse c).

  At this time, the measuring apparatus of the present invention measures the amount of the protic solvent in the sample based on the nuclear magnetic resonance signal acquired by the small RF coil, and the current of the sample. A switching unit that switches between a first measurement mode and a second measurement mode for measuring the amount of the protic solvent in the sample. When in the first measurement mode, the current calculation unit is configured to switch the small RF Calculation of the current at the specific location of the sample based on the difference between the frequency of the nuclear magnetic resonance signal acquired by the coil and the frequency of the oscillating magnetic field for excitation, and when in the second measurement mode, the solvent A quantity calculation part can be set as the structure which calculates the quantity of the protic solvent in the said specific location in the said sample based on the said nuclear magnetic resonance signal acquired with the said small RF coil.

  In this way, by switching between the first and second measurement modes, it becomes possible to measure the amount of local protic solvent in the sample in a short time in addition to the current measurement.

More specifically, in the second measurement mode, the small RF coil acquires an echo signal corresponding to the excitation oscillating magnetic field, and the solvent amount calculation unit calculates the T ₂ relaxation time from the intensity of the echo signal. A constant can be calculated, and the amount of the protic solvent at a specific location in the sample can be calculated from the calculated T ₂ relaxation time constant.

As described above, in the measurement method of the present invention, two physical quantities can be measured for a specific portion of the sample by a single pulse sequence in one measurement apparatus. For example, in the present invention, in the first step, the small RF coil applies the excitation oscillating magnetic field in a pulse sequence including the (a), (b) and (c), and (a) The FID signal corresponding to the pulse of (b) or the echo signal corresponding to the pulse of (c) is acquired, and in the second step, the FID signal corresponding to the pulse of (a) or (b) Alternatively, the difference between the frequency of the nuclear magnetic resonance signal and the frequency of the oscillating magnetic field for excitation is calculated using the real part and the imaginary part of the echo signal corresponding to the pulse of (c), and (b) and The T ₂ relaxation time constant is calculated from the intensities of a plurality of echo signals corresponding to the pulse of (c), and the calculated T ₂ relaxation time constant is applied to the specific location in the sample. The amount of the protic solvent can also be calculated. More specifically, the current can be measured with the first pulse corresponding signal in (b) above, and the water content can be measured using the n-th pulse corresponding signal group in (c).
The measurement of the two physical quantities may be performed at the same time, or may be performed at different timings such as alternating. For example, in the second step, the acquisition of an echo signal for calculating the difference between the frequency of the nuclear magnetic resonance signal and the frequency of the oscillating magnetic field for excitation, and the echo signal for calculating the T ₂ relaxation time constant Acquisition may be performed alternately. In the second step, the acquisition of an echo signal for calculating the difference between the frequency of the nuclear magnetic resonance signal and the frequency of the oscillating magnetic field for excitation, and the echo signal for calculating the T ₂ relaxation time constant Acquisition may be performed simultaneously.

In the above configuration, a small RF coil was used to obtain (i) an excitation oscillating magnetic field locally and (ii) an echo signal emitted from a location where the excitation oscillating magnetic field was applied. The T ₂ relaxation time constant (transverse relaxation time constant) is obtained from the echo signal, and the moisture content is measured based on this. Since the pulse echo method is applied by limiting the part to be measured with a small RF coil, the local water content can be measured in a short time.

In the present invention, the 90 ° pulse may be in the first phase, and the n number of 180 ° pulses may be in the second phase shifted by 90 ° from the first phase. In an actual measurement system, magnetic field inhomogeneities of the static magnetic field and the excitation oscillating magnetic field occur, which may cause a measurement error of the T ₂ relaxation time constant. The pulse sequence having the above configuration uses a 180 ° pulse that is in a second phase that is 90 ° shifted from the first phase. By applying the 180 ° pulse, the nuclear magnetization is reversed in the rotating coordinate system. This eliminates the measurement error factor derived from the magnetic field inhomogeneity. Since the second phase 180 ° pulse is applied periodically, the measurement error factor is eliminated each time, so that an accurate T ₂ relaxation time constant can be obtained with certainty.

In the present invention, a plurality of the small RF coils are provided, and in the second measurement mode, an excitation oscillating magnetic field is applied to a plurality of locations of the sample and an echo signal corresponding to the excitation oscillating magnetic field is acquired, The T ₂ relaxation time constant may be calculated for a plurality of locations on the sample, and the moisture content at the plurality of locations on the sample may be obtained based on the T ₂ relaxation time constant. Furthermore, it is good also as a structure which shows the moisture content distribution of the said sample based on the moisture content in the said several places of the said sample, after calculating | requiring the moisture content in the said several places.

  Further, in the measurement apparatus of the present invention, the easy movement of the protic solvent in the sample based on the gradient magnetic field application unit that applies a gradient magnetic field to the sample and the nuclear magnetic resonance signal acquired by the small RF coil. A mobility calculation unit for calculating the mobility, and a switching unit for switching between a first measurement mode for measuring the current of the sample and a third measurement mode for measuring the mobility of the protic solvent in the sample. In the third measurement mode, the small RF coil applies the excitation oscillating magnetic field to the sample, acquires a nuclear magnetic resonance signal corresponding to the excitation oscillating magnetic field and the gradient magnetic field, and A mobility calculation unit may calculate the mobility of the specific portion of the sample based on information of the nuclear magnetic resonance signal obtained corresponding to different gradient magnetic fields.

  In the measurement method of the present invention, a third step of applying an excitation oscillating magnetic field and a gradient magnetic field to a specific location of the sample and acquiring a nuclear magnetic resonance signal generated at the specific location; A fourth step of calculating the mobility of the specific portion of the sample based on the information of the nuclear magnetic resonance signal obtained in the step and the information of the nuclear magnetic resonance signal obtained in the third step; In the first step and the third step, a local magnetic field is applied to a specific location of the sample using the small RF coil, and a nuclear magnetic resonance signal is acquired from the specific location, In the first step, a gradient magnetic field is applied to the sample according to a predetermined pulse sequence, and the third step is different from the first step. It may be performed according to the gradient magnetic field a predetermined pulse sequence applied in the.

  In this way, by switching between the first and third measurement modes, it is possible to measure not only the current but also the mobility of the protic solvent at a specific location in the sample.

  Further, in the above configuration, using a small RF coil, (i) the excitation oscillating magnetic field and the gradient magnetic field are locally applied, and (ii) the excitation oscillating magnetic field and the gradient magnetic field are applied. A nuclear magnetic resonance signal is acquired, and the mobility at a specific location of the sample is measured from the NMR signal obtained corresponding to different gradient magnetic fields. The spin-echo method and the gradient magnetic field NMR method are applied with a small RF coil to limit the area to be measured, so the local mobility of the protic solvent in a predetermined region of the sample can be measured in a short time be able to.

  The “mobility” measured by the present invention refers to a physical property value indicating the ease of movement of a protic solvent in a sample. Such physical property values include parameters such as self-diffusion coefficient and mobility (movement speed). According to the present invention, any of these parameters can be obtained.

  In the present invention, the “different gradient magnetic field” includes a case where one gradient magnetic field is zero, that is, a measurement performed without applying a gradient magnetic field. For example, the first step may be performed without applying a gradient magnetic field.

  Moreover, in this invention, a gradient magnetic field application part can take a various aspect. For example, it can be a gradient magnetic field application coil disposed away from the small RF coil, or a planar coil provided in the same plane as the small RF coil. Moreover, it is good also as a pair of gradient magnetic field application coil arrange | positioned on both sides of a small RF coil. Alternatively, these configurations may be arbitrarily combined.

  For example, in the present invention, the planar shape of the pair of gradient magnetic field application coils may be approximately a half-moon shape, and the half-moon strings may be arranged to face each other toward the small RF coil side. By doing so, high-accuracy local measurement can be performed while saving space. In this specification, “substantially meniscus” means that a pair of planar coils has a string-like linear region, and a gradient magnetic field that is inclined in a direction perpendicular to the linear region is applied to the sample by arranging them in opposition to each other. If the gradient magnetic field can be applied, the planar shape of the moon shape of the coil may be larger or smaller than half a month.

  In the present invention, the sample may contain a matrix made of a solid or a gel. At this time, the solvent amount calculation unit and the mobility calculation unit can be configured to calculate the amount and mobility of the protic solvent contained in the matrix, respectively. Examples of such a sample include a film containing moisture, for example, a solid electrolyte film used for a fuel cell or the like.

  In addition, in the present invention, by adopting a configuration in which the amount of protic solvent or mobility at a specific location in the sample in addition to the current can be measured, the phenomenon occurring at the specific location of the sample can be grasped from various perspectives. It becomes possible. In particular, when applied to measurement of a solid electrolyte membrane of a fuel cell, it is possible to accurately grasp the current in the power generation state and the presence state of the protic solvent.

Moreover, in this specification, a protic solvent means the solvent which dissociates itself and produces a proton. Examples of protic solvents include water;
Alcohols such as methanol and ethanol;
Carboxylic acids such as acetic acid;
Phenol; and liquid ammonia. Among these, water and alcohol are solvents that can more easily measure the mobility or the amount of solvent in the present invention.

  It should be noted that any combination of these components, or a conversion of the expression of the present invention between a method, an apparatus, and the like is also effective as an aspect of the present invention.

  As described above, according to the present invention, the current at a specific portion of the sample can be measured locally.

It is a flowchart which shows the measurement procedure of the electric current in embodiment. It is a figure explaining the compensation function of CPMG method. It is a flowchart which shows the measurement procedure of the moisture content in embodiment. It is a figure for demonstrating the principle which acquires an NMR signal by a spin echo method. It is a figure which shows the example of the pulse sequence of a self-diffusion coefficient measurement. It is a flowchart which shows the measurement procedure of the self-diffusion coefficient in embodiment. It is a figure which shows schematic structure of the measuring apparatus in embodiment. It is a figure which shows an example of LC circuit which performs the application of the oscillating magnetic field for excitation of a measuring apparatus in embodiment, and the detection of a NMR signal. It is a figure which shows the structure of the switch part of the measuring apparatus in embodiment. It is a figure explaining the gap | deviation of the phase difference of a NMR signal. It is a perspective view which shows the example of arrangement | positioning of several small RF coil of the measuring apparatus in embodiment. It is a figure which shows the structure of the output part of the measuring apparatus in embodiment. It is a figure which shows schematic structure of the measuring apparatus in embodiment. It is a figure which shows the structure of the control part of the measuring apparatus in embodiment. It is a flowchart which shows the measurement procedure in embodiment. It is a figure which shows schematic structure of the measuring apparatus in embodiment. It is a figure which shows the structure of G coil of the measuring apparatus in embodiment. It is a flowchart which shows the measurement procedure in embodiment. It is a figure which shows schematic structure of the measuring apparatus in embodiment. It is a figure explaining the measuring method of the electric current in an Example. It is a figure which shows the sample used in the Example. It is a figure which shows the echo signal in an Example. It is a figure which shows the time change of the phase difference in an Example. It is a figure which shows the echo signal in an Example. It is a figure which shows the time change of the phase difference in an Example. It is a figure which shows the echo signal in an Example. It is a figure which shows the time change of the phase difference in an Example. It is a figure which shows the relationship between the electric current and frequency shift in an Example. It is a figure which shows the echo signal in an Example. It is a figure which shows the time change of the phase difference in an Example. It is a figure which shows the relationship between the electric current and frequency shift in an Example. It is a figure explaining the measuring method of the electric current in an Example. It is a figure which shows a part of structure of the measuring apparatus of the electric current in an Example. It is a figure explaining the measuring method of the electric current in an Example. It is a figure which shows the relationship between the electric current and frequency shift in an Example. It is a figure which shows the relationship between the electric current and frequency shift in an Example. It is a figure which shows the relationship between the electric current and frequency shift in an Example. It is a figure which shows the relationship between the electric current and frequency shift in an Example. It is a figure which shows the relationship between the electric current and frequency shift in an Example. It is a figure which shows the relationship between the electric current and frequency shift in an Example. It is a figure which shows the structure of the measuring apparatus in embodiment. It is a figure which shows the time change of the FID signal in an Example. It is a figure which shows the time change of the phase difference in an Example. It is a figure explaining the time change of the phase difference in an Example. It is a figure which shows the time change of the FID signal in an Example. It is a figure which shows the time change of the phase difference in an Example. It is a figure which shows the time change of the phase difference in an Example. It is a figure which shows the time change of the FID signal in an Example. It is a figure which shows the time change of the phase difference in an Example. It is a figure which shows the time change of the phase difference in an Example. It is a figure which shows the time change of the FID signal in an Example. It is a figure which shows the time change of the phase difference in an Example. It is a figure which shows the time change of the phase difference in an Example. It is a figure which shows the relationship between the electric current and frequency shift in an Example. Is a diagram showing the direction of the static magnetic field H ₀ and magnetic field H _i used in the analysis in Examples. It is a perspective view which shows the position of the copper plate in the magnetic field analysis in an Example, RF detection coil, and a water sample. It is a figure which shows the coordinate system used for the magnetic field analysis in an Example. It is a figure which shows the analysis result in an Example. It is a figure which shows the relationship between frequency shift amount (DELTA) omega and the electric current I in an Example. It is a figure which shows the structure of the small surface coil used in the Example. It is a figure which shows the relationship between the electric current I and the frequency shift amount (DELTA) omega in an Example. It is sectional drawing which shows schematic structure of MEA in an Example. It is a figure which shows the electric current which flows through the collector electrode and PEM in an Example. It is a figure which shows the analysis result of frequency shift amount (DELTA) omega in an Example. It is a figure which shows the structure of the small surface coil used in the Example. It is a figure which shows the coil placed on the carbon mesh in an Example. It is a figure which shows the measurement result of frequency shift amount (DELTA) omega in an Example. It is sectional drawing which shows schematic structure of MEA used for the analysis in a present Example. It is a figure which shows the analysis result of the frequency shift amount in an Example. It is sectional drawing which shows schematic structure of MEA in an Example. It is a figure which shows the frequency shift obtained by the measurement and analysis in an Example. It is sectional drawing which shows arrangement | positioning of MEA and a small coil in an Example. It is a figure which shows the measurement timing of PGSE and CPMG in an Example. In PGSE measurement of an Example, it is a figure which shows the time change of the electric current which flowed through MEA. It is a figure which shows the time change of the voltage applied to MEA in PGSE measurement of an Example. It is a figure which shows the measurement result of the frequency shift amount in the PGSE measurement of an Example, and the analysis result of a frequency shift amount. It is a figure which shows the time change of the frequency shift amount in the PGSE measurement of an Example. It is a figure which shows the time change of the echo signal intensity | strength measured with the anode side coil in the CPMG measurement of an Example. It is a figure which shows the time change of the echo signal intensity | strength measured with the cathode side coil in the CPMG measurement of an Example. It is a figure which shows the relationship between the water content in PEM in an Example, and signal strength. It is a figure explaining the phenomenon which has arisen in PEM at the time of the water electrolysis driving | operation of MEA in an Example.

  Embodiments of the present invention will be described below with reference to the drawings. In all the drawings, common constituent elements are denoted by the same reference numerals, and description thereof is omitted as appropriate.

(Measurement principle)
First, a measurement principle of a current measurement method in an embodiment described later will be described with an example. Hereinafter, the current measurement mode is also referred to as a first measurement mode.

(A) Current Measurement FIG. 1 is a flowchart showing an outline of a current measurement procedure. In FIG. 1, the following steps are sequentially performed, and a current at a specific portion of the sample is locally measured using a nuclear magnetic resonance (NMR) method. In the NMR method, the motion of nuclear magnetization can be detected as an NMR signal by the spin resonance phenomenon of a nucleus placed in a magnetic field. If an NMR signal is measured using a small surface coil (small RF coil), local NMR measurement of the coil periphery can be performed.
Step 301: Place the sample in a space where a magnet is arranged, and apply a static magnetic field to the sample.
Step 303: Applying an excitation oscillating magnetic field to a specific location of a sample placed in a static magnetic field using a small RF coil smaller than the sample, and acquiring a nuclear magnetic resonance (NMR) signal generated at the specific location. ,
Step 305: Calculate the difference between the frequency of the nuclear magnetic resonance signal acquired in step 303 and the frequency of the oscillating magnetic field for excitation.
Step 307: Obtain the current at a specific part of the sample from the difference obtained in Step 305. Step 309: Output the result thereafter.
Hereinafter, steps 303 to 307 will be described in detail.

(I) Step 303 (Application of excitation high-frequency pulse and acquisition of NMR signal)
In this step, a high frequency pulse applied to the measurement target nucleus in the sample is applied as the excitation oscillating magnetic field. Further, an NMR signal emitted from the measurement target nucleus in the sample is acquired by the nuclear magnetic resonance phenomenon caused by the excitation oscillating magnetic field.

Specifically, the NMR signal is an echo signal corresponding to the high frequency pulse for excitation. The phase of the echo signal is preferably converged so that the frequency difference in step 305 can be obtained reliably. Moreover, it is preferable to apply the high frequency pulse in a pulse sequence in which the phases of the echo signals are matched.
A specific example of such a pulse sequence will be described later with reference to FIG.

  The NMR signal is detected by separating the real part and the imaginary part by a phase sensitive detection method. Thereby, the calculation of the frequency difference in step 305 is easily performed.

(Ii) Step 305 (Calculation of frequency change)
In this step, the difference (frequency shift) between the frequency of the NMR signal acquired in step 303 and the frequency of the oscillating magnetic field for excitation is obtained.

  Specifically, the phase difference Δφ is obtained by calculating the arctan of the real part and the imaginary part of the echo signal acquired by the phase sensitive detection method. Then, the frequency shift Δω is converted as a phase difference Δφ per unit time.

(Iii) Step 307 (calculation of current)
In this step, the current is calculated from the frequency difference Δω acquired in step 305. Hereinafter, the calculation principle of the current will be described.

When a current flows through the measurement target, a magnetic field H _{j that} is directly proportional to the current _j is generated from Bio-Savart's law. The magnetic field strength is inversely proportional to the distance r ⁿ (where n is a power) between the position where the current flows and the measurement position.

  On the other hand, in the nuclear magnetic resonance phenomenon, the resonance frequency ω of nuclear magnetization is directly proportional to the magnetic field strength H. When the magnetic resonance signal is acquired by the small detection coil, the magnetic field intensity H in the region measured by the small detection coil is indirectly measured as the magnetic resonance frequency ω.

If the current _j is made to flow in the spatially and temporally stable magnetic field vector H ₀ created by the magnet to create the magnetic field vector H _j , the magnetic field strength H _j at a certain position is the combined vector (H ₀ + H _j ). Since the magnetic field vector H ₀ is constant, if the resonance frequency ω of the nuclear magnetization was increased or decreased by Δω, the magnetic field intensity H _j at a certain position it will be related to the current j and the distance r ^n.

  Therefore, for example, by acquiring in advance an experimental method or the like the relationship between the current j flowing in a specific location of the sample and the frequency difference Δω, the current flowing in the sample from the frequency difference Δω obtained in step 305. j can be obtained.

  Furthermore, by arranging a plurality of small coils on the sample and measuring the increase / decrease Δω of the resonance frequency of the nuclear magnetization at a plurality of positions in the sample, the current j and the position r through which it flows can be obtained by inverse problem analysis. it can.

  At this time, the NMR detection method has a frequency resolution on the order of ppm, and this makes it possible to capture changes in magnetic field strength with high resolution and high sensitivity. For example, when the frequency of the excitation oscillating magnetic field is 43 MHz, a resolution of about 10 Hz is sufficiently obtained.

Hereinafter, a specific example of the high frequency pulse for excitation applied in step (i) above will be described.
In actual measurement, magnetic field non-uniformity due to sample and device characteristics occurs, and the frequency difference may not be obtained accurately. Therefore, in the following embodiment, the spin echo method is used, and the excitation high-frequency pulse is a pulse sequence including a plurality of pulses including, for example, the following (a) and (b).
(A) a 90 ° pulse, and
(B) 180 ° pulse applied after elapse of time τ of the pulse of (a)

  By applying the excitation oscillating magnetic field according to the pulse sequences (a) and (b) above, the phase of the echo signal converges, and the measurement error due to such magnetic field inhomogeneity is effectively reduced. Moreover, since the variation in the phase of the corresponding echo signal can be suppressed, the current can be obtained more accurately. Hereinafter, the reason will be described with reference to FIG.

4, the resonance excited magnetization vector M _-y is slide into relaxation over time. The time change of the magnetic resonance signal actually observed at this time is relaxed by the spin-lattice relaxation time constant T ₁ and another time constant T ₂ ^* that cannot be expressed by the spin-spin relaxation time constant T ₂ alone. To go. This state is shown at the bottom of FIG. 4 immediately after the 90 ° excitation pulse as a change in signal intensity with time. In general, the actually measured magnetic resonance signal intensity indicated by the wavy line is rapidly attenuated, and its time constant T ₂ ^* is shorter than T ₂ . The reason why the decay signal actually observed decays faster than the decay curve due to T ₂ relaxation is because of the non-uniformity of the external static magnetic field created by the static magnetic field magnet and the non-uniformity of the magnetic field in the sample due to the magnetic properties and shape of the sample. This is because a uniform magnetic field is not ensured over the entire sample due to uniformity or the like. Such a time change of the actually measured magnetic resonance signal is referred to as free induction decay, “Free Induction decay” in English notation, and “FID” in abbreviated English notation.

There is a “spin echo” as a method for correcting a phase shift due to magnetic field inhomogeneity as a sample or device characteristic. This is because, after τ time of the 90 ° excitation pulse, a 180 ° excitation pulse having twice the excitation pulse intensity is applied, and the phase of the magnetization vector M is disturbed on the xy plane. This is a method of reversing and converging the phase after 2τ time to obtain an echo signal on the T ₂ attenuation curve.

When the direction along the static magnetic field is the Z direction for convenience, the 180 ° excitation pulse applied in the above (b) can be used in either the X direction or the Y direction.
Note that a 180 ° pulse may be further applied after the elapse of time 2τ in (b) above, and current measurement may be performed using an echo signal corresponding thereto. However, when current measurement is performed using a plurality of echo signals, it is effective to irradiate the 180-degree excitation pulse in the Y-axis direction a plurality of times so that the strongest possible echo signal can be observed. The reason is shown in the movement of the magnetization vector in FIGS. 2A to 2D described later.

  By adopting these methods, the phase of the magnetization vector can be converged and an echo signal as strong as possible can be obtained. With such an echo signal, the NMR signal can be detected with higher accuracy in the real part and the imaginary part, and the amount of phase change from the reference frequency can be reliably obtained.

The principle of current measurement has been described above.
Next, the measurement principle of the protic solvent amount in the sample using the NMR method and the ease of movement of the protic solvent amount (mobility) is taken as an example when the protic solvent is water. I will explain. These can be measured using a current measuring device, as will be described later in the fourth and fifth embodiments. In the following description, detailed description of steps common to the above-described current measurement will be omitted as appropriate.

First, a method for measuring the amount of moisture will be described. Hereinafter, the moisture amount measurement mode is also referred to as a second measurement mode.
(B) Measurement of water content In the following embodiment, the T ₂ (lateral) relaxation time constant is calculated by the CPMG (Carr-Purcell-Meiboom-Gill) method described later, and then “T ₂ and water content” The local moisture content of the sample is calculated using the conversion table, and the moisture content distribution is grasped.

FIG. 3 is a flowchart showing an outline of moisture content measurement.
Also in the moisture content measurement shown in FIG. 3, as in the current measurement described above, first, the sample is placed in the space where the magnet is arranged, and a static magnetic field is applied to the sample (S102). In this state, an excitation oscillating magnetic field (high frequency pulse) is applied to the sample via a small RF coil, and an NMR signal (echo signal) corresponding to this is acquired (S104).

Next, a T ₂ relaxation time constant is calculated from this echo signal (S106). Then, the local moisture content in the sample is measured from the obtained T ₂ relaxation time constant (S108). Specifically, data indicating the correlation between the amount of water in the sample and the T ₂ relaxation time constant is acquired, and the local amount of water at a specific location in the sample is obtained from this data and the T ₂ relaxation time constant. Ask for. Thereafter, the result is output (S110). By performing the above procedure (step 104 to step 110) through each small RF coil, the distribution of moisture content can be grasped.

Hereinafter, step 104 to step 108 will be specifically described.
(I) Step 104 (Application of excitation high-frequency pulse and acquisition of NMR signal)
The excitation high frequency pulse in step 104 is preferably a pulse sequence composed of a plurality of pulses, and an echo signal group corresponding to the pulse sequence is acquired. By doing so, the T ₂ relaxation time constant can be accurately obtained.

The pulse sequence preferably includes the following (a), (b) and (c).
(A) a 90 ° pulse, and
(B) 180 ° pulse applied after time τ of pulse (a), and (c) n 180 ° applied at intervals of time 2τ, starting from time 2τ of pulse (b). Pulse (n is a natural number)
The above (a) and (b) are common to (A) current measurement.

  By applying the excitation oscillating magnetic field according to the pulse sequences (a) to (c) above, the phase of the echo signal converges, and the measurement error due to such magnetic field inhomogeneity is effectively reduced. In addition, since the variation in the phase of the corresponding echo signal can be suppressed, the amount of moisture can be obtained more accurately. Hereinafter, this reason will be described with reference to FIGS. 2 (a) to 2 (d).

  A hydrogen nucleus placed in a static magnetic field has a net magnetization vector in a direction along the static magnetic field (for convenience, the Z direction), and an RF wave having a specific frequency (referred to as a resonance frequency) is transmitted along the Z axis. By irradiating from the outside in the X-axis direction perpendicular to the magnetic field, the magnetization vector is tilted in the positive direction of the Y-axis, and a nuclear magnetic resonance signal (referred to as NMR signal) can be observed. At this time, the excitation pulse in the X-axis direction irradiated to acquire the maximum intensity NMR signal is referred to as a 90 ° pulse. Then, after the magnetization vector is tilted in the positive direction of the Y axis by the 90 ° pulse, a 180 ° excitation pulse is irradiated from the outside in the “Y axis direction” after τ time, and the magnetization vector is set to “Y axis as the symmetry axis”. "Invert. As a result, after 2τ time, the magnetization vector converges on the “positive direction” of the Y axis, and an NMR signal having a large amplitude is observed.

  Thus, since the magnetization vector is inverted “with the Y axis as the axis of symmetry”, the following compensation function appears. FIG. 2A to FIG. 2D are diagrams for explaining the compensation function of the spin echo method. The coordinates shown in the figure are a rotating coordinate system.

  Consider P and Q as nuclear magnetization in a small region in the sample where the inhomogeneity of the static magnetic field is negligible. Let the magnetic field at P be stronger than the magnetic field at Q. At this time, as shown in FIG. 2A, when a 90 ° pulse is applied in the x′-axis direction, the nuclear magnetization of P and Q starts precession from the same location (y′-axis) in the rotating coordinate system. As time passes, the phase of P advances from the phase of Q (FIG. 2B).

  Therefore, when a 180 ° pulse is applied in the y′-axis direction after a time τ has elapsed from the 90 ° pulse, the nuclear magnetization of P and Q rotates 180 ° around the y′-axis, and before the pulse is applied, y ′ The arrangement is symmetric with respect to the axis (FIG. 2C).

  In this arrangement, since the nuclear magnetization P having a more advanced phase has a phase delayed from Q, both nuclear magnetizations simultaneously reach the y ′ axis at the time when the time τ has passed since then ( FIG. 2 (d)).

  Since such a relationship holds for the nuclear magnetization of all regions in the sample, all the nuclear magnetization gathers on the y ′ axis at this time, and as a result, a large NMR signal is obtained.

  As described above, by first applying a 90 ° pulse in the x′-axis direction and then applying a 180 ° pulse in the y′-axis direction, as shown in FIG. Reverses in the x'y 'plane. The compensation function is satisfactorily exhibited by the reversal of the nuclear magnetization. For example, the positions of P and Q have shifted to positions above or below the x'y 'plane due to (a) non-uniformity of the magnetic field and (b) non-uniformity of the excitation pulse intensity irradiated by the RF coil. Even in this case, the phase shift is compensated by reversing the nuclear magnetization in the x′y ′ plane.

As described above, after 2τ time, the magnetization vector converges on the “positive direction” of the Y axis, and an echo signal having a large amplitude is observed. Furthermore, in the above (c), the magnetization vector is irradiated with a 180 ° excitation pulse from the outside in the “Y-axis direction” after 3τ hours, and converged again on the “positive direction” of the Y-axis, and after 4τ hours. An echo signal with a large amplitude is observed. Further, irradiation with 180 ° pulses is continued at the same 2τ interval. During this time, the peak intensity of the even-numbered echo signals of 2τ, 4τ, 6τ,... Is extracted and fitted with an exponential function in step 106 to calculate the T ₂ (lateral) relaxation time constant by the CPMG method. Can do.

(Ii) Step 106 (calculation of T ₂ relaxation time constant)
The T ₂ relaxation time constant can be accurately measured by using the spin echo method described above with reference to FIG. The intensity SSE of the echo signal when using the spin echo is expressed by the following equation (A) in the case of TR >> TE.

  In the above formula (A), ρ is the density distribution of the target nuclide as a function of the position (x, y, z), TR is the 90 ° excitation pulse repetition time (about 100 ms to 10 s), and TE is the echo time (2τ, A is a constant representing device characteristics such as RF coil detection sensitivity and an amplifier.

In step 106, as described above, by fitting a plurality of echo signal groups (2τ, 4τ, 6τ,...) On the T ₂ attenuation curve acquired in step 104 with an exponential function, the above equation is obtained. From (A), the T ₂ relaxation time constant can be obtained.

(Iii) Step 108 (calculation of water content)
Returning to FIG. 3, in step 108, the water content is calculated from the T ₂ relaxation time constant. The amount of water in the sample and the T ₂ relaxation time constant have a positive correlation, and the T ₂ relaxation time constant increases as the amount of water increases. Since this correlation varies depending on the type and form of the sample, it is desirable to prepare a calibration curve for a sample of the same type as the sample to be measured whose moisture concentration is known in advance. That is, it is desirable to measure the relationship between the moisture content and the T ₂ relaxation time constant for a plurality of standard samples with known moisture content, and obtain a calibration curve representing this relationship in advance. By referring to the calibration curve created in this way, the amount of water in the sample can be calculated from the measured T ₂ relaxation time constant.

Next, calculation of mobility will be described. The mobility measurement mode is hereinafter also referred to as a third measurement mode.
(C) Calculation of mobility In the following embodiment, by applying a gradient magnetic field and measuring the self-diffusion coefficient of water molecules by the PGSE (Pulsed-Gradient Spin-Echo) method, local water molecules of the sample are measured. The mobility of water molecules is calculated and the distribution of the mobility of water molecules is grasped.

  After exciting a specific nuclear spin in a liquid molecule by magnetic resonance and applying a pair of gradient magnetic field pulses (pulsed gradient magnetic field) at intervals of several tens of ms, individual nuclei move in a Brownian motion or The phase of the nuclear spin does not converge due to the movement due to diffusion, so that the intensity of the NMR signal decreases. The self-diffusion coefficient of a specific molecular species can be measured by associating the gradient magnetic field pulse changed stepwise with the decrease in the intensity of the NMR signal. This is the principle of measuring the self-diffusion coefficient by the PGSE method.

  FIG. 5 is a diagram illustrating an example of a PGSE sequence used for measuring the self-diffusion coefficient. In the sequence shown in FIG. 5, a pair of gradient magnetic field pulses Gz having the same intensity as the application time are applied in the z direction to the spin echo sequence described above with reference to FIG. For example, a spin echo signal is acquired.

The peak intensity S of the obtained NMR signal depends on the applied pulse gradient magnetic field intensity Gz [gauss / m], the application time d, and the pulse interval Δ, and the self-diffusion coefficient Dz [m in the z direction is expressed by the following relational expression. ² / s].
ln (S / S ₀ ) = − γ ² DzΔ ² dGz ² (II)

In the above formula (II), S ₀ represents a normal NMR signal intensity when Gz = 0. D, Δ, and Gz represent the pulse width of the gradient magnetic field pulse, the time interval between the pair of gradient magnetic field pulses, and the magnetic field gradient (z direction) of the gradient magnetic field pulse, respectively. Γ represents the gyromagnetic ratio and is a value specific to the nucleus. For example, in the case of the hydrogen nucleus 1H, the magnetic rotation ratio is 42.577 × 10 ² [1 / gauss · s].

  FIG. 5 illustrates a sequence when d = 1.5 ms and Δ = 34.5 ms. For example, by applying a magnetic field to the sample in such a pulse sequence, the self-diffusion coefficient Dz can be stably calculated using the peak intensity S of the NMR signal.

FIG. 6 is a flowchart for measuring the mobility of a specific portion of the sample using the PGSE method as described above, and includes the following steps.
First, a sample is placed in a static magnetic field created by a magnet or the like, and a static magnetic field is applied to the sample. In this state, an excitation oscillating magnetic field is applied to the sample according to a predetermined pulse sequence through the small RF coil, and an NMR signal corresponding to the excitation magnetic field is acquired through the small RF coil (S202).

  Next, an oscillating magnetic field for excitation and a gradient magnetic field are applied to the same region in the sample, and an NMR signal corresponding to this is acquired via a small RF coil (S204).

  FIG. 6 is a flow when no gradient magnetic field is applied in step 202, but application of a gradient magnetic field having a magnitude different from that in step 204 may be executed in step 202 according to a predetermined pulse sequence. At this time, for example, the magnitude of the gradient magnetic field in step 202 is preferably set to a value close to zero.

Subsequently, the self-diffusion coefficient D is calculated from a plurality of NMR signals obtained by changing the gradient of the pulse gradient magnetic field stepwise (S206). In addition, after step 206, based on the self-diffusion coefficient D calculated in step 206, a parameter indicating other mobility of water in the sample may be calculated. Thereafter, the result is output (S208).
By performing such an operation (step 202 to step 208) through each small RF coil, the distribution of the self-diffusion coefficient can be grasped.

Details of each step will be described below.
(I) Step 202 and Step 204 (application of excitation oscillating magnetic field, application of gradient magnetic field and acquisition of NMR signal)
In step 202 and step 204, an excitation oscillating magnetic field and a gradient magnetic field are applied to the sample according to a predetermined pulse sequence. The excitation oscillating magnetic field is a pulse sequence composed of a plurality of pulses, and the gradient magnetic field is a pair of pulse sequences corresponding to the excitation oscillating magnetic field.

  Regarding the gradient magnetic field, as described above, in step 202, the gradient magnetic field is set to zero or a value close to zero, and in step 204, a predetermined gradient magnetic field is applied.

Moreover, it is preferable that a pulse sequence shall consist of the following (a)-(d).
(A) a 90 ° pulse of an oscillating magnetic field for excitation,
(B) A gradient magnetic field pulse that starts after the elapse of the pulse time of (a) and is applied for a fixed time d,
(C) a 180 ° pulse of an oscillating magnetic field for excitation applied after elapse of time τ of the pulse of (a), and
(D) A gradient magnetic field pulse that starts after the elapse of the pulse time of (c) and is applied for a predetermined time d.
However, when the gradient magnetic field is set to zero in step 202, the sequence (b) is not performed.

  More specifically, as shown in FIG. 5 described above, the time when the application of the gradient magnetic field pulse (b) is completed and the time when the application of the gradient magnetic field pulse (d) is started are 180 in (c). ° Pulse (the pulse has a width of 120 microseconds. The central 60 microseconds is considered as the axis of symmetry), and equal time ((34.5 ms-1.5 ms) /2=16.5 ms) Further, the application time d of the gradient magnetic field pulse (b) and the application time d of the gradient magnetic field pulse (d) are both equal (d = 1.5 ms).

  Then, an NMR signal corresponding to the pulse sequence is measured. The peak intensity S of the NMR signal is measured by a spin echo method. Specifically, as shown in FIG. 5, the peak intensity S of the echo signal that appears at 2τ time is measured. The peak intensity S may be not only the NMR signal intensity for 2τ hours, but also the average value of the NMR signal intensity measured in the surrounding time. By this method, it is possible to reduce variations in measured values caused by noise included in the NMR signal.

  In this way, by applying a gradient magnetic field stepwise and detecting the degree of decrease in the NMR signal corresponding to an increase in the magnetic field gradient, the self-diffusion coefficient D of protons in the sample is calculated.

  In step 204, the step of applying the excitation oscillating magnetic field and the gradient magnetic field according to a predetermined pulse sequence and the step of acquiring the NMR signal corresponding to this pulse sequence are executed once or a plurality of times.

(Ii) Step 206 (Measurement of self-diffusion coefficient D)
In step 206, the self-diffusion coefficient D of water at a specific location of the sample is obtained from the peak intensity of the NMR signal obtained in steps 202 and 204. The proton self-diffusion coefficient D is expressed by the above-described formula (II) using the peak intensity S of the NMR signal obtained by the PGSE method.

From the peak intensity S ₀ of the NMR signal when the gradient magnetic field G is not applied and the peak intensity S of the NMR signal when the gradient magnetic field G is applied, the self of protons in the sample is obtained using the above formula (II). A diffusion coefficient D can be obtained. For example, by measuring the same location in the sample while changing the magnitude of the gradient magnetic field G and plotting the relationship between ln (S / S ₀ ) and -γ ² DΔ ² dG ² , the gradient of the plot is self- A diffusion coefficient D can be obtained.

  Note that (B) measurement of moisture content and (C) mobility measurement described above may be measured by switching measurement modes. Further, the distribution of the amount of movement of water molecules can be calculated based on the amount of water calculated in each measurement mode and the mobility of water.

  Hereinafter, a method for measuring a local current using the above-described measurement principle and an apparatus for realizing the method will be described in more detail.

(First embodiment)
FIG. 7 is a diagram illustrating a schematic configuration of the measurement apparatus 300 according to the present embodiment. Each component of the measuring apparatus 300 is realized by an arbitrary combination of hardware and software, centering on a CPU, a memory, a program that implements the components shown in FIG. It will be understood by those skilled in the art that there are various modifications to the implementation method and apparatus.

The measuring device 300 is a device that locally measures the current at a specific location of the sample 115 using the NMR method,
A sample mounting table 116 on which a sample 115 is mounted;
A static magnetic field application unit (magnet 113) for applying a static magnetic field to the sample 115;
A small RF coil 114 smaller than the sample 115 that applies an oscillating magnetic field for excitation to the sample 115 and acquires an NMR signal generated at a specific location of the sample 115, and
A current calculation unit 303 is provided that calculates a difference Δω between the frequency of the NMR signal acquired by the small RF coil 114 and the frequency of the excitation oscillating magnetic field, and calculates a current at a specific location of the sample 115 from the difference.

In addition, the measurement apparatus 300 includes an RF oscillator 102, a modulator 104, an RF amplifier 106, a preamplifier 112, a detector 301, an A / D converter 118, a switch unit 161, a pulse control unit 108, a time measuring unit 128, a sequence. A table 127, a calculation unit 130, a data reception unit 131, a storage unit 305, an output unit 135, and the like are provided.
Moreover, the measuring apparatus 300 may be provided with the structure mentioned later with reference to FIG.

  The sample 115 is a sample to be measured. The sample 115 can be in various forms such as a solid such as a film or a lump, a liquid, agar, a gel such as a jelly. In the case of a membranous substance, the measurement result of the local water content can be stably obtained. In particular, when a film having a property of retaining moisture in the film, such as a solid electrolyte film, is used as a sample, the measurement result can be obtained more stably.

The sample mounting table 116 is a table on which the sample 115 is mounted, and a sample having a predetermined shape and material can be used.
The magnet 113 applies a static magnetic field to the sample 115 (S301 in FIG. 1). The excitation oscillating magnetic field is applied to the sample in a state where the static magnetic field is applied, and the current is measured.

  The small RF coil 114 applies an excitation oscillating magnetic field to a specific portion of the sample 115 and acquires an NMR signal corresponding to the excitation oscillating magnetic field (S303 in FIG. 1). Specifically, the NMR signal is a high-frequency pulse for the excitation oscillating magnetic field to generate nuclear magnetic resonance.

  There may be a single RF coil 114 or a plurality of small RF coils 114 arranged inside the sample, on the sample surface or in the vicinity of the sample. A configuration in which a plurality of small RF coils 114 are arranged will be described later in the second embodiment.

  The small RF coil 114 is preferably ½ or less of the size of the entire sample, and more preferably 1/10 or less. By setting it as such a size, it becomes possible to measure the local mobility of the protic solvent in a sample correctly in a short time. The size of the sample can be, for example, a projected area when the sample is placed, and the exclusive area of the small RF coil 114 is preferably ½ or less of the projected area, more preferably 1 By setting it to / 10 or less, accurate measurement can be performed in a short time. The size of the small RF coil 114 is preferably, for example, 10 mm or less in diameter.

  As the small RF coil 114, for example, the one shown in FIG. 33A described later in the embodiment can be used. By using the planar coil as shown in the figure, the measurement region can be limited and local measurement can be performed. The measurement area of such a spiral coil has a width of about the diameter of the coil and a depth of about the coil radius. Further, since this coil has a flat shape unlike a normal solenoid type coil, an NMR signal can be obtained simply by pasting it on a flat sample.

  Further, the small RF coil 114 is not limited to a flat spiral coil, and various types can be used. For example, a planar 8-shaped coil (sometimes referred to as a butterfly coil, a Double-D coil, or the like) can be used. The figure 8 coil includes two spiral coils, and the NMR signal from the sample can be obtained even when the spiral axis of the coil is parallel to the direction of the main magnetic field of the magnet or when both have an angle. Can be detected. In addition, the spiral coil has sensitivity in the axial direction of the wound coil, whereas the 8-shaped coil has sensitivity in the same plane as the wound coil.

  Returning to FIG. 7, the oscillating magnetic field (exciting oscillating magnetic field) applied by the small RF coil 114 includes the RF oscillator 102, the modulator 104, the RF amplifier 106, the pulse control unit 108, the switch unit 161, and the small RF coil 114. Generated by cooperation. In the present embodiment, the RF pulse generation unit that generates an RF pulse for generating an oscillating magnetic field for excitation in the small RF coil 114 includes the RF oscillator 102, the modulator 104, and the RF amplifier 106. The excitation oscillating magnetic field oscillated from the RF oscillator 102 is modulated by the modulator 104 based on the control by the pulse control unit 108 and becomes a pulse shape. The generated RF pulse is amplified by the RF amplifier 106 and then transmitted to the small RF coil 114.

  The reference frequency is set to the resonance frequency of the NMR signal in a state where no current flows. This resonance frequency is stored in the RF oscillator 102.

  Further, the pulse control unit 108 controls the above cooperation so that the excitation oscillating magnetic field applied to the sample 115 by the small RF coil 114 is executed according to the above pulse sequence.

  The pulse control unit 108 is connected to the sequence table 127 and the time measuring unit 128, and generates a high frequency pulse based on the sequence data acquired from the sequence table 127 and the measurement time in the time measuring unit 128. The sequence table 127 stores high-frequency pulse sequence data when current is measured. Specifically, the sequence table 127 stores a timing diagram in which the generation time and interval of the high-frequency pulse are set, and the intensity of the high-frequency pulse to be applied based on the timing diagram.

  The small RF coil 114 applies this RF pulse to a specific location of the sample 115 placed on the sample placement table 116. Then, the small RF coil 114 acquires the NMR signal of the applied RF pulse. The NMR signal is, for example, an echo signal corresponding to the excitation oscillating magnetic field. The frequency of the echo signal changes from the reference frequency described above due to the magnetic field formed by the flow of current. For this reason, the current flowing through the sample 115 is obtained from the difference in the frequency of the measured echo signal by acquiring in advance the relationship between the frequency variation (difference) and the current value. The frequency difference is obtained by converting the amount of phase change at a certain time interval per unit time.

An oscillating magnetic field for excitation applied to the sample 115 by the small RF coil 114 is, for example,
(A) a 90 ° pulse, and
(B) A pulse sequence composed of 180 ° pulses applied after the elapse of time τ of the pulses in (a).

  In the case where the small RF coil 114 is used, it may be difficult to adjust the excitation pulse intensity of the above (a) and (b). For example, in the region to be measured, that is, the region surrounded by the small RF coil 114, a difference occurs in the excitation method between the central portion and the peripheral portion, so that the entire excitation angle is uniform. That is, it may be difficult to excite so that the intensity ratio of the excitation magnetic field in (a) and (b) is constant. If the excitation angle ratio in (a) and (b) varies, an appropriate spin echo signal cannot be acquired, and accurate measurement of current becomes difficult.

  Therefore, in such a case, in addition to the above pulse sequence, the pulse control unit 108 adds another sequence in which a step of applying a 180 ° pulse at a time τ before the 90 ° pulse (a) is added. Make it run. Then, by comparing the behavior of the attenuation curve of the 180 ° pulse (b) corresponding to these two sequences, whether the excitation pulse intensity of the 90 ° pulse (a) and the 180 ° pulse (b) is accurate or not. Can be determined. As a result, even when the excitation pulse intensity is deviated due to an abnormality of the apparatus, the abnormality can be detected at a stage before the measurement is performed, and the measurement value can be made more accurate. Further, (a) the 90 ° pulse is in the first phase, and (b) the 180 ° pulse is in the second phase that is 90 ° shifted from the first phase.

Next, detection of NMR signals will be described.
The NMR signal detection unit detects the NMR signal acquired by the small RF coil 114 and sends the NMR signal to the calculation unit 130. The NMR signal detector includes a preamplifier 112, a detector 301, and an A / D converter 118. The detected NMR signal is amplified by the preamplifier 112 and then sent to the detector 301.

The detector 301 is configured to detect a real part and an imaginary part of the NMR signal by a phase sensitive detection method. In order to accurately separate the NMR waveform acquired by the detector 301 into a real part and an imaginary part, the phase difference between the sine wave and the cos wave of the fundamental wave that is the source of demodulation is precisely 90 degrees. It is preferable to adjust. By adjusting so that the two fundamental waves have a phase difference of exactly 90 degrees, the phase difference can be calculated more accurately using tan ⁻¹ of the real part and the imaginary part described later. Note that the reference wave that is the source of demodulation is generated by, for example, a 90 ° hybrid described later with reference to FIG.

  The detector 301 sends the detected real part and imaginary part to the A / D converter 118. The A / D converter 118 A / D-converts the NMR signal and sends it to the data receiving unit 131. The calculation unit 130 including the current calculation unit 303 acquires the data sent to the data reception unit 131.

The application of the excitation oscillating magnetic field and the detection of the NMR signal have been described above. However, these can be realized by an LC circuit including a small coil.
FIG. 8 is a diagram illustrating an example of such an LC circuit. In FIG. 8, the coil portion (inductance portion) of the resonance circuit is a small RF coil having a diameter of 1.4 mm. In the nuclear magnetic resonance (NMR) method, the atomic number density and the spin relaxation time constant can be measured by detecting the movement of nuclear magnetization as an NMR signal by the spin resonance phenomenon of a nucleus placed in a magnetic field. The spin resonance frequency in a magnetic field of 1 Tesla is about 43 MHz, and an LC resonance circuit as shown in FIG. 8 is used to selectively detect the frequency band with high sensitivity.

Returning to FIG. 7, the switch part 161 is provided in a branch part connecting the small RF coil 114, the RF amplifier 106 and the preamplifier 112.
A first state in which the small RF coil 114 and the RF signal generator (RF amplifier 106) are connected; and
It has a function of switching the second state in which the small RF coil 114 and the NMR signal detector (detector 301) are connected. That is, the switch unit 161 serves as a “transmission / reception switching switch”. The role is to transmit the excitation pulse amplified by RF power-amp to the small RF coil 114 to separate the preamplifier 112 of the receiving system and protect it from a large voltage, and to receive the NMR signal after excitation. In other words, the noise generated by the large amplification transistor leaking from the RF amplifier 106 is blocked from being transmitted to the preamplifier 112 of the receiving system. When measurement is performed using the small RF coil 114, a weak signal is handled, so the switch unit 161 is necessary for the following reason. On the other hand, in a large measurement system that does not use the small RF coil 114, the use of a “cross diode” can sufficiently cope. The cross diode is a diode that is turned on when a voltage equal to or higher than a predetermined value is applied and is turned off when the voltage is lower than the predetermined value.

The reason why the “transmission / reception switching switch”, that is, the switch unit 161 is particularly necessary when the small RF coil 114 is used is as follows.
(I) The sample volume that can be detected by the small coil of this measurement system is smaller than that of the large coil. This detectable sample volume is approximately (coil inner area × coil radius depth). In order to measure a weak NMR signal that decreases in proportion to the volume with low noise and high sensitivity, it is necessary to block noise leaking from the large amplification transistor of the RF amplifier 106 in the transmission system. . In the receiving system, it is necessary to use a highly sensitive preamplifier 112. In using the high-sensitivity preamplifier 112, the preamplifier 112 must be disconnected so that the preamplifier 112 can be protected from a high-voltage excitation pulse sent to a small coil during transmission.
(Ii) When exciting the nuclear magnetization in the sample volume, with a suitable excitation pulse power, specifically, the relationship between the intensity of the 90-degree pulse and the 180-degree pulse is 1: 2, or the irradiation energy is 1: 4. Alternatively, it is necessary to excite nuclear magnetization so that the pulse application time has a one-to-two relationship. If the excitation pulse power cannot be adjusted properly, the target spin echo pulse sequence will not be obtained, and as a result, an appropriate spin echo signal cannot be acquired. Decreases. This phenomenon is prominent when switching between transmission and reception of a small coil using a conventional cross diode. In the case of a large coil, the excitation pulse intensity is very large and the loss in the cross diode can be considered to be negligibly small, but in the case of a small coil, the excitation pulse intensity is smaller than that of the large coil, so The loss of can not be ignored. For this reason, in order to obtain an appropriate excitation pulse intensity, a “transmission / reception selector switch” with as little loss as possible is required.

  By providing the switch part 161 at the branch part, the loss of the oscillating magnetic field signal applied to the sample 115 from the small RF coil 114 is reduced, and as a result, the pulse angles of the 90 ° pulse and the 180 ° pulse are accurately set. It becomes possible to control. Accurate control of the pulse angle is an important technical problem in reliably obtaining a compensation effect in the spin echo method. In the present embodiment, this problem is solved by the arrangement of the switch unit 161.

  In addition, the RF detection coil for local measurement is miniaturized, and the reduction in noise during NMR reception is an important factor for ensuring the accuracy of measurement. When receiving an NMR signal, noise that enters the preamplifier 112 mainly includes an RF wave transmission system, which is caused by “RF wave leakage” or “high power amplifier” from the RF amplifier 106 that amplifies the excitation pulse. There is "noise". When receiving the NMR signal, it is necessary to reliably block the excitation wave leaking from the transmission side by the switch unit 161 and receive the NMR signal with low noise. In the present embodiment, this problem is also solved by the arrangement of the switch unit 161.

  The switch unit 161 can employ various configurations. FIG. 9 is a circuit diagram showing an example of the configuration of the switch unit 161.

The apparatus configuration around the sample has been described above. Next, an NMR signal processing block will be described.
Returning to FIG. 7, the real part and the imaginary part of the NMR signal (echo signal) detected by the detector 301 are acquired by the data reception unit 131 and sent to the calculation unit 130. The calculation unit 130 includes a current calculation unit 303. The current calculation unit 303 acquires the real part and the imaginary part of the echo signal detected by the detector 301, calculates the phase difference between the echo signal and the excitation oscillating magnetic field using these, and based on this phase difference, The difference (frequency shift amount) Δω between the frequency of the signal and the frequency of the excitation oscillating magnetic field is calculated (S305 in FIG. 1).

Specifically, tan ⁻¹ (Re / Img) is calculated from the detected real part and imaginary part. This value corresponds to the phase difference ΔΦ [rad] of the NMR signal. As shown in FIG. 10, ΔΦ is a phase difference between a reference wave (phase Φ ₀ ) traveling at a frequency that does not change with time and the measured NMR signal. Here, the reference frequency is set in advance to the resonance frequency of the NMR signal when no current flows.

  The current calculation unit 303 obtains Δω from the amount of change per unit time of the obtained phase difference ΔΦ. Then, the current value of the sample 115 at the measurement location is calculated by referring to the relationship between Δω and the current (S307 in FIG. 1). The current calculation unit 303 may calculate the current density by dividing the obtained current value by the area where the current flows.

  Here, the measurement apparatus 300 includes a storage unit 305 that stores information indicating a correlation between a current and a difference in frequency for each type of the sample 115. The storage unit 305 stores, for example, data on the correlation between the frequency difference Δω and the current obtained experimentally. More specifically, this is calibration curve data of the frequency difference Δω and the current. The current calculation unit 303 in the calculation unit 130 acquires calibration curve data corresponding to the sample to be measured from the storage unit 305, and calculates a current corresponding to the frequency difference Δω based on the calibration curve data.

  The current calculated by the current calculation unit 303 is presented to the user by the output unit 135 (S309 in FIG. 1). Various forms of presentation are possible, and there are no particular restrictions on display on the display, printer output, file output, and the like.

  41 shows the RF oscillator 102, the modulator 104, the RF amplifier 106, the pulse control unit 108, the switch unit 161, the small RF coil 114, the preamplifier 112, the detector 301, and the A / D conversion in the measurement apparatus 300 shown in FIG. It is a figure which shows the example of a further detailed structure about cooperation of the device 118. FIG. This configuration can also be applied to the measuring apparatus shown in FIGS. 13 and 16 described later.

  41, the modulator 104 includes a mixer 177, a mixer 179, and a synthesizer 181. The detector 301 includes a mixer 183, a mixer 185, and a distributor 187. The A / D converter 118 includes a first A / D converter 189 and a second A / D converter 191.

  In FIG. 41, a 90 ° hybrid 171 and a distributor 173 are further arranged in this order between the RF oscillator 102 and the modulator 104, and a distributor 175 is further provided between the 90 ° hybrid 171 and the detector 301. Is arranged.

  In this configuration, the waveforms output from the RF oscillator 102 are made into two waveforms having the same frequency but different phases by 90 ° by the 90 ° hybrid 171. Based on these two reference waveforms, the NMR signal is detected and becomes Real and Imaginary components.

  Here, the two waveforms output from the 90 ° hybrid 171 are specifically a sine wave and a cosine wave, and it is important for obtaining the phase that the two waveforms are accurately orthogonal to each other. is there.

  In FIG. 41, the names of the signals in the A / D converter 118 are named Real and Imaginary, but this is a representation for convenience and may be reversed to Imaginary and Real. In the opposite case, the phase obtained by arctan is merely shifted by ± 90 °, and this is not a problem when obtaining the “phase change amount” that increases and decreases with time.

Further, the “NMR signal intensity” required when determining the moisture content and mobility described later in the fourth and fifth embodiments is based on the acquired Real and Imaginary components.
(Real ^ 2 + Imaginary ^ 2) ^-1/2
Can be converted to that intensity. That is, this calculation corresponds to obtaining the radius of the circle in FIG.

Next, the effect of this embodiment is demonstrated.
When a small surface coil is used as in this embodiment, since the measurement region is small, the static magnetic field uniformity in the measurement region is high, and the echo signal can be observed over a very long time. Thereby, the frequency shift amount can be measured with high frequency resolution.

  Further, by converging the phase of the NMR signal using the spin echo method, the phase of the echo signal can be converged and acquired by the small RF coil 114. Thereby, the real part and the imaginary part of the echo signal can be detected, and the phase difference ΔΦ using them can be calculated more accurately. Note that the measurement of the frequency shift amount in this embodiment and other embodiments of this specification may not use the spin echo method, and the frequency shift amount is calculated from a simple FID (Free Induction Decay). You can also. In the spin echo method, since the measurement region is limited to be smaller than that of the FID, the uniformity of the static magnetic field can be further improved as compared with the FID.

  In addition, when attempting to measure the entire sample with a large solenoid coil instead of the small RF coil 114 when measuring the current, the uniformity of the static magnetic field deteriorates, the FID is short, the echo is short, and the sharp peak It becomes a shape. For this reason, it is difficult to perform with a large solenoid coil due to the uniformity of the magnetic field. On the other hand, since the small RF coil 114 is used in this embodiment, sufficient magnetic field uniformity can be obtained.

  In the chemical shift method, it is also possible to measure the frequency shift amount of the NMR signal by using a large solenoid coil and applying a gradient magnetic field to excite only a specific local area. On the other hand, in the small surface coil, since the measurement region is limited by the shape of the coil, it is not necessary to use a gradient magnetic field for local excitation. For this reason, an apparatus structure can be simplified.

  Further, when using the Hall element described above with reference to Non-Patent Document 2, it is necessary to measure two physical quantities of the sensor resistance value and temperature, whereas in the method of the present embodiment, from the nuclear magnetic resonance signal, Since it suffices to acquire the obtained frequency, it is a simple method in that only one physical quantity needs to be measured.

  Further, in NMR measurement using a small surface coil, a static magnetic field may be created using a rod-shaped magnet, and the sensor unit is small and can be used as a current measurement probe that can be easily installed in the apparatus. In addition, as will be described later in the fourth and fifth embodiments, “water content” and “mobility of water molecules” in a sample such as a polymer film can be locally measured at the same place almost simultaneously. it can.

This embodiment and the following embodiments can be applied to, for example, local current measurement of a solid electrolyte membrane of a fuel cell.
In addition, even if the current j measured by the method of the above embodiment is a current that flows in a state where the fuel cell is generating power, or a current when a direct current voltage is applied and a water electrolysis operation is performed The principle of forming a magnetic field is the same. Therefore, by measuring the increase / decrease Δω of the resonance frequency, it is possible to grasp the spatial current during power generation and water electrolysis operation of the fuel cell.

  In a fuel cell using a solid polymer electrolyte membrane, the power generation state changes depending on the gas supply state, catalyst deterioration, and ionic conductivity of the polymer electrolyte membrane. When the hydrogen utilization rate is increased, the hydrogen concentration is high near the gas supply port and the generated current at that location is large, while the hydrogen concentration is low near the gas outlet and the generated current is also small. This is because the “mass transport loss” increases.

  In addition, if the catalyst of the fuel cell deteriorates, the “activation loss” increases and the generated current decreases. The Pt catalyst deteriorates due to transient fluctuations such as starting and stopping of the fuel cell, which causes spatial non-uniformity. Further, depending on the water content of the polymer electrolyte membrane, the ionic conductivity increases and decreases, the “ohm loss” changes, and the generated current increases and decreases. Since this loss depends on the spatial distribution of moisture content, the current also has a spatial distribution even within a single polymer electrolyte membrane.

  In fuel cell power generation, the above-mentioned “material transport loss”, “activation loss”, and “ohm loss” overlap to determine the current and voltage that are finally output, which is the battery performance. The current output from the output terminal of the fuel cell can be easily measured with an ammeter, but the current value is a planar “total of MEA (Membrane Electrode Assembly)”, and the current with a spatial distribution is planar. This is the integrated value. The information inside the battery necessary for improving the battery performance is a power generation state that varies from place to place, and a current that varies from place to place. Furthermore, if the water content, the mobility of water molecules, and the gas concentration can be measured for each location, the phenomenon occurring inside the battery can be grasped in more detail.

  If the spatial distribution of the current in the MEA plane can be measured, the power generation state at each location can be determined, and the state of “material transport loss”, “activation loss”, and “ohm loss” in space can be determined. Specifically, it can be seen where the power generation state increased or decreased when the gas supply concentration, hydrogen utilization rate, gas supply pressure, humidification amount, or moisture content of the membrane was changed, and the resulting battery performance increased or decreased. You can investigate in detail. Thus, technical guidelines for improving battery performance can be obtained. Measuring the spatial distribution of current in the MEA plane is required for developing high-performance fuel cells.

  According to this embodiment, the spatial current of the fuel cell can be grasped by measuring the increase / decrease Δω of the resonance frequency.

Note that, in the measuring apparatus 300, in addition to the measurement of current, it is possible to obtain the T ₂ relaxation time constant using the CPMG method, thereby calculating the moisture content of the sample.
Further, by providing the measuring apparatus 300 with a gradient magnetic field coil and applying a gradient magnetic field to the sample as appropriate, the mobility of the target molecule can be measured by using the PGSE method to which the gradient magnetic field is applied.
These measurements will be described in fourth and fifth embodiments described later.

(Second embodiment)
The measuring apparatus 300 described in the first embodiment may include a plurality of small RF coils 114. In the present embodiment, the plurality of small RF coils 114 apply an excitation oscillating magnetic field to a plurality of locations of the sample 115 and acquire nuclear magnetic resonance signals. The current calculation unit 303 is configured to calculate currents at a plurality of locations of the sample 115.
FIG. 11 is a perspective view showing an arrangement example of a plurality of small RF coils 114.

  By providing a plurality of small RF coils 114 in the apparatus, the current distribution in the sample 115 can be measured. In this case, if it is two-dimensionally arranged along the surface of the sample 115, a two-dimensional current distribution on the sample surface can be obtained. Further, if the sample 115 is three-dimensionally arranged, a three-dimensional current distribution in the sample can be obtained.

  For example, the calculation unit 130 may include a current distribution calculation unit (not shown) that calculates the current distribution in the sample 115 based on the calculation result of the current in the current calculation unit 303. Thereby, the excitation oscillating magnetic field can be applied to a plurality of locations of the sample and the NMR signals corresponding thereto can be acquired. A current distribution calculation unit (not shown) calculates a current distribution in the sample based on currents at a plurality of locations in the sample. The output unit 135 outputs this distribution.

  In the present embodiment, the output unit 135 may be configured as shown in FIG. In FIG. 12, the output unit 135 and the measurement data acquisition unit 135 </ b> A that acquires the current for each measurement region of the plurality of small RF coils 114 (FIG. 11) calculated by the current calculation unit 303 and the acquired current on the same screen. A display unit 135B for displaying in the partitioned area.

  In the display unit 135B, as shown in FIG. 11, the screen is divided into a plurality of regions according to the arrangement position of the small RF coil 114. Each area is displayed in a predetermined color according to the current in the measurement area of each small RF coil 114.

  In this way, by displaying the color corresponding to the current in the measurement region of each small RF coil 114 in each region of the display unit 135B, the relationship between the measurement position in each small RF coil 114 and the current is intuitive. I can grasp it. Thereby, it can be set as the measuring apparatus convenient for a user.

  Furthermore, the plurality of regions of the display unit 135B may be divided into two parts, one above the other (for example, the upper half), and the amount of moisture in the sample 115 at the corresponding location may be shown in the lower half. Measurement of the amount of water in the sample 115 will be described later in the fourth embodiment.

  Moreover, the measuring apparatus 300 described in the first embodiment may be an apparatus that acquires a current distribution in a plane of a solid polymer electrolyte membrane of a fuel cell by using a nuclear magnetic resonance method. At this time, the sample 115 is a solid polymer electrolyte membrane of a fuel cell. In addition, the current distribution acquisition unit (current distribution calculation unit) determines, for a plurality of small RF coils 114, the difference (frequency shift amount) between the frequency of the nuclear magnetic resonance signal acquired by the small RF coil 114 and the frequency of the oscillating magnetic field for excitation. Δω) is calculated, and an in-plane current distribution of the solid polymer electrolyte membrane is obtained from Δω.

Further, when the measuring device 300 is a measuring device for a fuel cell, by obtaining Δω for a plurality of regions in the surface of the solid polymer electrolyte membrane or MEA (Membrane Electrode Assembly), the operating state of the fuel cell is obtained. Diagnosis is possible. For example, in each region, when Δω is measured and compared with a theoretical analysis value, if the measured value of Δω behaves differently from the analysis value only at a specific measurement location, The MEA may have a problem. In addition, when Δω is measured at a predetermined time interval for a plurality of measurement points, if the difference between the measured value and the analysis value of Δω becomes large at the whole measurement points, the output of the entire MEA decreases. It may have occurred.
Note that a method for obtaining Δω in a plurality of regions in the MEA plane will be described more specifically in an example described later.

(Third embodiment)
In the measurement apparatus 300 (FIG. 7), by providing a plurality of small RF coils 114, the measurement accuracy of the frequency shift amount Δω can be further increased by the following procedure.

  Here, when the current measurement method described above in the first embodiment is used, for example, as described later in the examples, first, “the frequency of nuclear magnetic resonance of water molecules without current (a state in which no current flows) ( This is referred to as a reference frequency), and then “the amount of shift of the nuclear magnetic resonance frequency when a current is passed” is obtained.

  In this method, when the reference frequency does not change (constant) over time (for example, when a superconducting magnet or an electromagnet is used as a magnet), the reference frequency only needs to be acquired at the beginning of the measurement. Thereafter, it is only necessary to perform measurement when a current is passed. In this case, there is an advantage that it is easy to measure time fluctuation and transient response of current.

  On the other hand, when a permanent magnet is used as the magnet, the magnetic field strength may fluctuate with time due to fluctuations in the temperature of the magnet. When the magnetic field strength fluctuates, the reference frequency cannot be said to be constant over time.

  In the case of such a fluctuating magnetic field (reference frequency), “measure the NMR signal with and without current at a time interval that is short enough to assume that the reference frequency does not change, and from the difference between the two, A method of “determining the amount of frequency shift” is conceivable. For example, in the examples described later, this method is selected and the time interval is set to 10 seconds.

  However, for example, when the above embodiment is used for measurement of a fuel cell, the fuel cell does not immediately enter a steady state even if it starts power generation and starts flowing current, and it takes several seconds to several minutes to reach a steady state. There is. In addition, it may be difficult to apply current measurement in a “slowly occurring phenomenon” in which the load varies, the gas supply varies, or moisture condensation occurs in the gas diffusion layer. This is because the above-described “NMR measurement with no current at a short time interval at which the reference frequency can be regarded as constant” cannot be performed.

Therefore, in the present embodiment, the following (i) and (ii) are combined to estimate the reference frequency when there is no current, thereby calculating the frequency shift amount.
(I) A plurality of RF coils are used. One coil is placed at a position where measurement is desired, and the other RF coil is placed at a "position away from the fuel cell so that the influence of the magnetic field generated by the current can be ignored".
(Ii) “The magnetic field distribution (nuclear magnetic resonance frequency) in the permanent magnet only rises and falls uniformly in the entire space. If the variation of the nuclear magnetic resonance frequency is measured at a certain point, It is possible to estimate if the nuclear magnetic resonance frequency of the place is raised or lowered by the fluctuation amount.

Moreover, in this embodiment, the some small RF coil 114 is arrange | positioned as follows. Here, a case of measurement of power generation of a fuel cell is shown as an example, but the following method can be applied to the type of the sample 115 without particular limitation.
(Coil 1) First small RF coil 114: An RF coil is placed at a location slightly away from the fuel cell (where the influence of the magnetic field due to current can be ignored), and the reference frequency is measured at a location where the coil can receive NMR signals. The sample 115 is placed and the nuclear magnetic resonance frequency in the magnet is measured. This serves as a “reference frequency monitoring RF coil and sample”.
(Coil 2) A plurality of remaining small RF coils 114: arranged at positions where the sample 115 is to be measured.

Then, measurement is performed using a system capable of receiving NMR signals with a plurality of coils.
(I) First, NMR signals in a “state in which no current flows” are received by all the small RF coils 114 (coil 1 and coil 2), and a magnetic field distribution (nuclear magnetic resonance frequency distribution ω) is obtained.
(I-1) The resonance frequency in the coil 1 is ω _monitor (t = 0). t is the time.
(I-2) The nuclear magnetic resonance function at the position x where the coil 2 is placed is ω (t = 0, x).
(Ii) The power generation in the fuel cell is started, and the NMR signal in the “current flowing state” is received by all the small RF coils 114 (coil 1 and coil 2). The time is t1.
(Iii) A fluctuation amount Δω of the reference frequency is obtained from the NMR signal acquired in (i).
The fluctuation amount Δω (t1) at time t1 is
ω _monitor (t1) −ω _monitor (t = 0)
It is.
(Iv) Using this fluctuation amount Δω (t1), the “reference frequency when there is no current” at the coil position of the coil 2 is estimated from the following equation.
ω _no-current (t1, x) = ω (t1, x) + Δω (t1)
(V) “The frequency of the NMR signal actually measured by the coil 2 when there is a current” is ω _current (t1, x).
The frequency shift amount Δω (t1, x) when there is current is
Δω (t1, x) = ω _current (t1, x)-ω _no-current (t1, x)
It can be calculated by The current distribution may be analyzed based on Δω (t1, x) obtained as described above.

According to this embodiment, in addition to the first embodiment, the following operational effects can be obtained.
That is, by measuring the NMR signals for coil 1 and coil 2 at the same time, the reference frequency can be estimated more accurately. Thereby, the measurement accuracy of the frequency shift amount Δω (t1, x) can be increased. For this reason, for example, when used for measurement of a fuel cell, it is not necessary to switch and measure the fuel cell between “no current in a short time”. Thereby, measurement in a more practical power generation situation can be performed.

Note that coil 1 and coil 2 need not be measured simultaneously. For example, the measurement may be performed by alternately switching the coil 1 and the coil 2. The reference frequency ω _no-current (t1, x) in the case of “no current” depending on the position where the coil is placed may be estimated with a certain degree of accuracy.

As described above, in the first to third embodiments, the measurement of the local current of the sample has been described.
In the following embodiments, a method and apparatus for measuring the amount or mobility of a protic solvent in a sample in addition to the local current of the sample will be described. The following embodiments are applicable to any of the first to third embodiments.

(Fourth embodiment)
In the present embodiment, current and water content are measured using a local magnetic resonance signal acquired by a small detection coil.

  FIG. 13 is a diagram illustrating a schematic configuration of the measurement apparatus of the present embodiment. The basic configuration of the apparatus shown in FIG. 13 is the same as that of the measuring apparatus 300 shown in FIG. 7 except that the calculation unit 130 is provided with a solvent information calculation unit 309. Further, a difference is that a control unit 307 is provided instead of the pulse control unit 108 of FIG.

  The solvent information calculation unit 309 calculates information regarding the solvent contained in the sample 115, and includes a water content calculation unit 132 in this embodiment. The moisture amount calculation unit 132 calculates the amount of the protic solvent (water) in the sample 115 based on the NMR signal acquired by the small RF coil 114.

FIG. 14 is a diagram illustrating a configuration of the control unit 307 of the apparatus illustrated in FIG.
In FIG. 14, in addition to the pulse control unit 108 described above, the control unit 307 switches between a first measurement mode for measuring the current of the sample 115 and a second measurement mode for measuring the moisture content in the sample 115 ( A mode switching control unit 169). The operation signal accepting unit 129 connected to the mode switching control unit 169 accepts the operator's request for the measurement mode. Then, the operation signal receiving unit 129 sends this request to the mode switching control unit 169.

  In the first measurement mode, the current of the sample 115 is measured according to the procedure described in the above embodiment. That is, the current calculation unit 303 calculates the current at a specific location of the sample 115 based on the difference between the frequency of the NMR signal acquired by the small RF coil 114 and the frequency of the excitation oscillating magnetic field.

In the second measurement mode, the small RF coil 114 acquires an NMR signal (echo signal) corresponding to the excitation oscillating magnetic field, and the solvent amount calculator 132 (moisture amount calculator 132) The amount of the protic solvent (water) in the sample 115 is calculated based on the echo signal acquired in step (1). Specifically, the moisture amount calculation unit 132 calculates the T ₂ relaxation time constant from the intensity of the echo signal, and calculates the amount of the protic solvent at a specific location in the sample 115 from the calculated T ₂ relaxation time constant. To do.

In the present embodiment, for example, a common pulse sequence is used for the first and second measurement modes.
That is, the small RF coil 114 applies the excitation oscillating magnetic field in a pulse sequence including the following (a) to (c).
(A) 90 ° pulse,
(B) 180 ° pulse applied after time τ of pulse (a), and (c) n 180 ° applied at intervals of time 2τ, starting from time 2τ of pulse (b). Pulse (n is a natural number)

  In the first measurement mode, the small RF coil 114 acquires an echo signal corresponding to the pulse (b) or (c). At this time, since the echo signal corresponding to the pulse (b) has the highest intensity, it is preferable to use this echo signal. Further, the current calculation unit 303 acquires the real part and the imaginary part of the echo signal, and calculates the current.

On the other hand, in the second measurement mode, the small RF coil 114 acquires a plurality of echo signals corresponding to the pulses (b) and (c). Further, the moisture amount calculation unit 132 calculates a T ₂ relaxation time constant from the intensities of the plurality of echo signals.

FIG. 15 is a flowchart illustrating an example of a procedure for measuring current and water content. This measurement method includes the following steps.
Step 301 (Step 102): Applying a static magnetic field to the sample 115,
Step 303 (Step 104): Applying an excitation oscillating magnetic field via the small RF coil 114 in a pulse sequence including the above (a) to (c), and obtaining an echo signal corresponding to this.
Step 305: Using the real part and the imaginary part of the echo signal corresponding to the pulse (b) or (c) acquired in step 303, the difference between the frequency of the echo signal and the frequency of the excitation oscillating magnetic field is calculated. ,
Step 307: From the difference obtained in Step 305, obtain the current at a specific location of the sample.
Step 106: Calculate a T ₂ relaxation time constant from the intensities of a plurality of echo signals corresponding to the pulses (b) and (c) acquired in Step 303.
Step 108: Measure the local water content in the sample from the T ₂ relaxation time constant calculated in Step 106.
Step 309 (Step 110): Thereafter, the result is output.

In step 303 (step 104), obtaining an echo signal for calculating the difference between the frequency of the nuclear magnetic resonance signal and the frequency of the excitation oscillating magnetic field, obtaining an echo signal for calculating the T ₂ relaxation time constant, May be performed simultaneously. For example, when using the above pulse (b) for calculating the frequency difference and calculating the T ₂ relaxation time constant, in step 303 (step 104), the pulse corresponds to the pulses (b) and (c). Acquire an echo signal. In step 305, the frequency difference is calculated using the real part and the imaginary part of the echo signal corresponding to the pulse (b). In step 307, a T ₂ relaxation time constant is calculated from the intensities of a plurality of echo signals corresponding to the pulses (b) and (c). Note that the pulse of (c) can be used for calculating the frequency difference and calculating the T ₂ relaxation time constant.

  According to the present embodiment, by a series of measurements using a common pulse sequence, it is possible to measure not only the local current of the sample 115 such as a membrane but also the water content with one apparatus. For this reason, the state of the sample 115 at the time of power generation or water electrolysis operation can be grasped in more detail.

In the present embodiment, the small RF coil 114 is an oscillating magnetic field for excitation in a pulse sequence in which a pulse for current measurement (first measurement mode) and a pulse for moisture measurement (second measurement mode) are alternately repeated a plurality of times. Can also be applied. That is, the acquisition of the echo signal for calculating the difference between the frequency of the nuclear magnetic resonance signal and the frequency of the excitation oscillating magnetic field and the acquisition of the echo signal for calculating the T ₂ relaxation time constant are performed alternately. You can also. In this way, the local current and water content of the sample 115 can be measured more stably.

(Fifth embodiment)
In the present embodiment, current, moisture content, and water mobility are measured using local magnetic resonance signals acquired by a small detection coil.

  FIG. 16 is a diagram illustrating a schematic configuration of the measurement apparatus of the present embodiment. The basic configuration of the apparatus illustrated in FIG. 16 is the same as that of the measurement apparatus illustrated in FIG. 13, but the solvent information calculation unit 309 of the calculation unit 130 further includes a mobility calculation unit 133, and the calculation unit 130. The difference is that a movement amount calculation unit 134 is provided. In addition to the apparatus shown in FIGS. 7 and 13, the apparatus shown in FIG. 16 has a gradient magnetic field application unit (a pair of G coils 151) that applies a gradient magnetic field to the sample 115 and a pair of G coils 151. Further, a current driving power source 159 for supplying a pulse current is provided.

  The pair of G coils 151 are gradient magnetic field application coils that are spaced apart from the small RF coil 114. As shown in FIG. 17, the pair of G coils 151 are arranged so that a gradient magnetic field can be applied to the sample 115. Two G coils 151 are arranged with respect to one small RF coil 114, and are opposed to each other with the small RF coil 114 interposed therebetween.

  Various shapes can be adopted for the G coil 151, but a flat coil is used in this embodiment. In this embodiment, the G coil 151 has a half-moon shape as shown in FIG. Note that FIG. 17 illustrates a case where a plurality of small RF coils 114 are provided in one sample 115 and a pair of G coils 151 are arranged for each small RF coil 114. The G coil 151 is arranged in parallel to the surface of the sample 115.

  The G coil 151 is disposed above the small RF coil 114. Thereby, a gradient magnetic field having a magnetic field gradient in the y-axis direction can be formed on the central axis of the small RF coil 114.

  A shielding shield (not shown) is provided between the small RF coil 114 and one G coil 151 and between the small RF coil 114 and the other G coil 151. This shielding shield prevents noise from the G coil 151 from affecting the small RF coil 114. The shielding shield has a thickness that prevents the passage of noise and allows a magnetic field to pass.

  Note that only the small RF coil 114 is brought into contact with the sample 115 when measuring the current, water content, and self-diffusion coefficient.

  Returning to FIG. 16, the mobility calculation unit 133 determines the mobility of the protic solvent (water) in the sample 115 based on the NMR signal acquired by the small RF coil 114 corresponding to the different gradient magnetic fields. Calculate gender.

  Further, the movement amount calculation unit 134 calculates the movement amount of water molecules based on the moisture amount calculated by the moisture amount calculation unit 132 and the self-diffusion coefficient calculated by the mobility calculation unit 133. The movement amount calculation unit 134 reads, for example, a parameter storage unit that stores parameters for calculating the movement amount of water molecules, and a calculation formula stored in the parameter storage unit, and calculates the movement amount of water molecules. A movement amount calculation unit.

  The parameter storage unit stores a calculation formula for calculating the amount of movement of water molecules from the self-diffusion coefficient and the amount of water for each sample 115 type. Based on this calculation formula, the movement amount calculation unit can calculate the movement amount.

  In the present embodiment, the mode switching control unit 169 in the control unit 307 includes a first measurement mode in which the current of the sample 115 is measured, a second measurement mode in which the amount of moisture in the sample 115 is measured, and Switch the third measurement mode to measure the water mobility.

  In the third measurement mode, the small RF coil 114 applies an excitation oscillating magnetic field to the sample 115 and acquires a nuclear magnetic resonance signal corresponding to the excitation oscillating magnetic field and the gradient magnetic field. In addition, the mobility calculation unit 133 calculates the mobility of a specific portion of the sample 115 based on the information of the nuclear magnetic resonance signals obtained corresponding to different gradient magnetic fields.

In the third measurement mode, the small RF coil 114 applies the excitation oscillating magnetic field in a pulse sequence including the following (a) to (d).
(A) a 90 ° pulse of an oscillating magnetic field for excitation,
(B) A gradient magnetic field pulse that starts after the elapse of the pulse time of (a) and is applied for a fixed time d,
(C) a 180 ° pulse of an oscillating magnetic field for excitation applied after elapse of time τ of the pulse of (a), and
(D) A gradient magnetic field pulse that starts after the elapse of the pulse time of (c) and is applied for a predetermined time d.

  Note that the gradient magnetic field applied in (b) may be zero. Further, (a) the 90 ° pulse is in the first phase, and (c) the 180 ° pulse is in the second phase that is 90 ° shifted from the first phase, the peak intensity of the NMR signal based on spin-spin A correlation with the self-diffusion coefficient D of water in the sample 115 can also be acquired.

FIG. 18 is a flowchart illustrating an example of a procedure for measuring current and mobility. FIG. 18 shows an example in which the gradient magnetic field applied in (b) in the pulse sequence is zero, and includes the following steps.
Step 301 (Step 102): Applying a static magnetic field to the sample 115,
Step 303 (Step 202): The gradient magnetic field is set to zero, the excitation oscillating magnetic field is applied in a pulse sequence including the above (a) to (d), and an echo signal corresponding to this is acquired (first step),
Step 305: Using the real part and the imaginary part of the echo signal corresponding to the pulse of (d) acquired in step 303, calculate the difference between the frequency of the echo signal and the frequency of the oscillating magnetic field for excitation.
Step 307: Obtain the current at a specific location of the sample from the difference obtained in Step 305 (second step),
Step 204: The gradient magnetic field is set to a non-zero predetermined magnitude, the excitation oscillating magnetic field is applied in a pulse sequence including the above (a) to (d), and an echo signal corresponding to this is obtained (third step).
Step 206: From the peak intensity of the NMR signal obtained in Step 202 and Step 204, the self-diffusion coefficient D of water at a specific location of the sample 115 is obtained using the above formula (II) (fourth step).
Step 309 (Step 208): Thereafter, the result is output.

  In this procedure, the current and self-diffusion coefficient D can be obtained by a series of measurements by setting the gradient magnetic field in step 202 to zero.

  In the apparatus shown in FIG. 16 as well, the current and moisture content of the sample 115 can be obtained by a single measurement by the procedure described above with reference to FIG.

  In this embodiment, in addition to the local current of the sample 115 such as a membrane, the water content and the mobility of water molecules can also be measured. For this reason, the state in the membrane at the time of power generation or water electrolysis operation can be grasped in more detail.

  In addition, by combining the above three measurement methods, for example, the “current distribution” in the fuel cell, the “water content” in the polymer electrolyte membrane, and the “mobility of water molecules” can be changed simultaneously or alternately. It can be measured. Measurement that integrates these is useful as an integrated monitoring method for fuel cells, and is effective as a device that provides new measurement quantities to development sites aimed at improving fuel cell performance and expands the application range of NMR sensors. It is.

According to the above embodiment, for example, the following effects can be obtained.
The amount of current flowing in a sample such as a fuel cell can be converted from the frequency shift amount of the NMR signal received by the small detection coil. At that time, even with one small detection coil, if the current flowing through the sample is uniform, the amount of current can be easily converted from the amount of frequency shift.
In addition, it is possible to incorporate multiple small detection coils in a single cell of an actual machine, acquire NMR signals from the polymer film, and convert the current distribution from the frequency shift amount Δω of the NMR signals generated when current flows. Become. This makes it possible to effectively measure the current distribution with a plurality of coils.
In addition, the “local moisture content”, “local mobility of water molecules”, and “current distribution” of the polymer membrane for fuel cells are locally measured by the same device at the same location with the same device. By alternately measuring the three quantities every few seconds, both values can be acquired at substantially the same time (same device, same position, almost same time).
In addition, it is possible to perform a short-time measurement in which the water content, the mobility of water molecules, and the current are measured within a few seconds.
Moreover, non-invasive measurement using electromagnetic waves is performed only by sticking on the surface of the polymer film.
In addition, the amount of water, the mobility of water molecules, and the current distribution can be measured while generating power from the fuel cell.
In addition, the state of the polymer membrane can be grasped from various information such as “water content”, “mobility of water molecules” and “current distribution”, and the power generation state or water electrolysis state in the fuel cell is monitored. Monitoring for controlling the power generation efficiency to be the highest is possible.
In addition, in the “bar-shaped local measurement sensor integrated with a magnet and a gradient magnetic field coil”, the sensor can be easily installed in the fuel cell, and only the RF detection coil section needs to be in the region to be measured. Measurement can be performed without obstruction (FIG. 19).
Further, by integrating the magnet and the coil, the limitation of applicability of the NMR method due to the apparatus configuration is solved, and the application range can be expanded to food management and process management other than the measurement of the polymer film.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

For example, in the above embodiment, the case where the frequency shift amount is measured using the spin echo method when measuring the current has been described as an example. However, as described later in the embodiment, the frequency shift amount is simple. It can also be calculated from FID (Free Induction Decay). When using FID, for example, a small RF coil 114 is used.
(A) A 90 ° pulse may be applied to obtain a FID signal corresponding to the 90 ° pulse, and the current calculation unit 303 may obtain a real part and an imaginary part of the FID signal and obtain a current from a phase change amount. . In this way, since measurement can be performed with only the 90 ° pulse, the repetition time of the excitation pulse can be shortened, and the amount of phase change can be obtained in a short time. Further, since the FID signal itself can be observed whether it is smaller or larger than 90 °, the adjustment can be simplified as compared with the spin echo method.
Moreover, also when measuring the moisture content or the water mobility together with the current, the current can be calculated from the FID signal corresponding to (a) by using the pulse sequence including the above (a).

Example 1
In this example, water was poured into a narrow gap, a copper plate was placed in close contact with the sample, and the change in frequency of the NMR signal when current was passed through the copper plate was measured.
FIG. 20 is a diagram for explaining the outline of the present embodiment. As shown in FIG. 20, in this example, an experiment was performed in which a current j was passed through a copper plate to form a magnetic field H _j, and the frequency change of the NMR signal from water placed on the side was measured. By this experiment, the relationship between the current j and the frequency shift amount Δω is acquired. The copper plate simulates a fuel cell, and the water simulates a polymer film in the fuel cell.

As a sample, two cover glasses having dimensions of 18 mm × 18 mm and a thickness of 0.12 mm were used to form a sealed container with a gap of 0.5 mm, and a 2.5 mmol / L CuSO ₄ aqueous solution was enclosed therein. . FIG. 21 is a diagram showing a sample (CuSO ₄ aq. 2.5 mmol / L) used in this example. A copper plate having dimensions of 20 mm × 20 mm and a thickness of 0.05 mm was placed immediately below the sample. A steady current j can be passed through the copper plate using a DC stabilized power supply. In a copper plate, the current j can be regarded as flowing uniformly in the plane.

  The NMR signal was measured by setting the interval between the 90 degree excitation pulse and the 180 degree excitation pulse to 5 ms and the echo time being 10 ms. In this sequence, a gradient magnetic field was applied for 1 ms before and after the 180 degree excitation pulse so that the NMR signals immediately after the 90 degree and 180 degree excitation pulses did not interfere with the echo signal.

  An echo signal when the current j is zero is shown in FIG. The NMR signal was detected by a phase sensitive detection method, and two signals of a real part and an imaginary part were obtained. In FIG. 22, the real part and the imaginary part are indicated by “Real” and “Imag”, respectively. The 90-degree excitation pulse was irradiated at time = 5 ms. “Power” in the figure is a signal intensity calculated from a real part and an imaginary part. From the form of “Power”, it can be seen that the echo takes a peak at time = 15 ms.

Based on the real part Re and the imaginary part Img, tan ⁻¹ (Re / Img) was taken to calculate the phase difference ΔΦ [rad] of the NMR signal. The phase reference is a reference wave from an oscillator included in the NMR apparatus, and this frequency is adjusted in advance to the resonance frequency of the NMR signal. The phase difference between the reference wave (phase Φ ₀ ) that does not change with time and the measured NMR signal was defined as ΔΦ. The relationship between the real part, the imaginary part, and the phase difference ΔΦ is shown in FIG.

FIG. 23 shows the phase difference ΔΦ calculated from tan ⁻¹ (Re / Img) in FIG. However, in this figure, only the time from 13 ms to 17 ms during which the echo signal is observed is shown.

  From FIG. 23, it can be seen that when the phase difference ΔΦ is substantially constant in time (straight line) and the current j is zero, the NMR signal rotates with a constant phase difference from the reference wave.

  Next, FIG. 24 shows an echo signal measured when the current j is 0.80 A, and FIG. 25 shows a phase difference ΔΦ calculated based on the echo signal. The pulse sequence is the same as when the current j is zero.

  In the echo signal of FIG. 24, unlike FIG. 22, it can be seen that the real part and the imaginary part of the NMR signal vibrate and the frequency deviates from the reference wave. In the area of the echo signal, the real part comes first and the imaginary part vibrates thereafter.

FIG. 25 shows the phase difference ΔΦ calculated by obtaining tan ⁻¹ (Re / Img) in FIG. In this figure, as time elapses, the phase difference ΔΦ increases (upward straight line), and it can be seen that the phase of the NMR signal advances from the reference wave as time elapses. Originally, the phase difference ΔΦ seems to be a single straight line that increases with time, but the phase is expressed in the range of 2π from -π to + π. It appears as a discontinuous line shifted by 2π. This is the reason for the discontinuous transition from + π to −π at time = 14.6 ms.

  Further, FIG. 26 shows an echo signal measured at −0.80 A when current j is applied in the reverse direction, and FIG. 27 shows a phase difference ΔΦ calculated based on this echo signal.

  In the echo signal of FIG. 26, it can be seen that the NMR signal of the real part and the imaginary part is inverted (vibrated first downward) and oscillates, and the frequency is shifted from the reference wave in the reverse direction. .

FIG. 27 shows the phase difference ΔΦ calculated by obtaining tan ⁻¹ (Re / Img) in FIG. In this figure, contrary to FIG. 25, it can be seen that the phase difference ΔΦ decreases (straight-down straight line) with the passage of time, and the phase of the NMR signal delays with the passage of time from the reference wave. .

  FIG. 28 shows the results of an experiment conducted in increments of 0.20 A with the current j flowing through the copper plate being changed from −0.80 A to +0.80 A. On the vertical axis of this figure, the phase difference ΔΦ of the NMR signal that changes during 1 ms is defined as “frequency shift amount Δω [rad / ms] of the NMR signal”. This “frequency shift amount Δω [rad / ms]” corresponds to the “slope of the phase difference ΔΦ” in FIGS. 23, 25, and 27, and the graph of the phase difference ΔΦ is linearly approximated by the method of least squares. It was calculated from the gradient.

  From this graph, it can be seen that the current j flowing through the copper plate and the frequency shift amount Δω [rad / ms] are in a directly proportional relationship. By using this result, the current j flowing through the copper plate can be calculated backward by measuring the shift amount Δω [rad / ms].

  The factor that increases or decreases the frequency of the NMR signal over time is not only the current j flowing through the copper plate, but also the increase or decrease of the magnetic field strength in the case of a permanent magnet. If the temperature of the permanent magnet increases or decreases, the magnetic field strength also increases or decreases in inverse proportion to it. For this reason, a time-stable magnetic field is required for frequency shift measurement.

  However, the permanent magnet has a large heat capacity, and a frequency change due to a rapid temperature change can be ignored if the time is about 1 minute. Therefore, in order to accurately measure the frequency shift amount of the NMR signal, the NMR signal when the current is zero is acquired, and the phase difference ΔΦ (j = 0) with the reference wave at that time is obtained in advance. Then (after 10 seconds in this experiment), the current j is applied to obtain the phase difference ΔΦ (j) when the current flows, and the phase difference substantially caused by the current is expressed as ΔΦ (j) − What is necessary is just to obtain | require with (DELTA) (PHI) (j = 0). In the measurement of the fuel cell, the phase difference when the current is changed by changing the load may be measured. By this method, the phase difference can be measured with higher accuracy.

  In addition, this method has a feature that even when the frequency of the reference wave is set to be slightly deviated from the true resonance frequency of the NMR signal, this “deviation” can be canceled by subtraction.

(Example 2)
In this example, the relationship between the current j and the frequency shift amount ΔΦ (j) during water electrolysis operation using MEA (Membrane Electrode Assembly) was verified.
The MEA is obtained by joining an electrode to a PEM (Polymer Electrolyte Membrane). The MEA used here was manufactured by electrolessly plating Pt and Ir on the anode side and Pt on the cathode side on a polymer electrolyte membrane manufactured by Asahi Glass. The dimensions of the MEA are 17 mm × 15 mm square and 500 μm thickness.

The MEA was standardized, pulled up from the ion exchange water just before the experiment, and wiped off the water appropriately. From the T ₂ (CPMG) relaxation time constant of MEA immediately before the water electrolysis operation, the water content of MEA was about 10 [H ₂ O / SO ₃ ⁻ H ⁺ ].

  The MEA was sandwiched between a polycarbonate cell with a small surface coil and a Pt electrode and energized. The voltage applied between both electrodes was 2 to 3.5 V, and the current j was 0.10 to 0.30 A. With this energization, the MEA decomposes water contained in the PEM and releases hydrogen and oxygen. In this experiment, water is not supplied during water electrolysis (non-humidified condition). The cell temperature was 24 ° C.

  FIG. 29 shows an echo signal measured when 0.30 A of current j is passed through the MEA, and FIG. 30 shows a phase difference ΔΦ calculated based on the echo signal. From FIG. 29 and FIG. 30, it can be seen that the echo signal acquired from the MEA progresses although the phase difference is slight with time.

  The experiment is performed in increments of 0.10 A with the current j flowing through the MEA being 0.0 A to +0.30 A, and FIG. 31 shows the relationship between the current j flowing through the MEA and the frequency shift amount Δω [rad / ms]. The method of organizing the results is the same as in FIG.

  It can be seen from FIG. 31 that the current j flowing through the MEA and the frequency shift amount Δω [rad / ms] are in a substantially direct relationship. If this result is used, the current j flowing through the MEA can be calculated backward by measuring the shift amount Δω [rad / ms].

  In addition, comparing FIG. 28 and FIG. 31, it can be seen that even when the same current j is applied, the frequency shift amount is small to about 1/4 in the case of the copper plate and the case of the MEA. The reason for this is that when the copper plate is energized, it is considered that the current flows uniformly, but in MEA, the electrical conductivity of the Pt catalyst electrode plated on the surface and the (Pt + Ir) catalyst electrode is non-uniform. For this reason, it is estimated that the current does not flow uniformly. For this reason, the small surface coil is measuring the part where the current of MEA is small, and it is guessed that the amount of frequency shift became small.

  As a method for further improving the measurement accuracy of this measurement method, there is a method of creating a calibration curve by measuring a current and a frequency shift amount using an MEA having a uniform electrical conductivity. In addition, by installing multiple small surface coils at multiple locations on the MEA, measuring the in-plane distribution of the frequency shift amount, and solving the current distribution as an inverse problem based on this, obtains a more accurate current distribution. May be.

(Example 3)
In the present embodiment, when two small coils are arranged in adjacent areas and measurement is performed, the amount of frequency shift corresponding to each area is measured, and the current value corresponding to each area can be measured. It was confirmed.

Specifically, NMR of water samples placed on two copper plates was measured using two small RF coils. At this time, the current values I ₁ and I ₂ flowing through the two copper plates are individually changed, and the relation between the frequency shift amount Δω of the NMR signal acquired simultaneously by the two coils and the current values I ₁ and I ₂ . Was experimentally determined.

An overall outline of the apparatus is shown in FIG. The water to be measured is sandwiched between two cover glasses (15 mm × 15 mm) and sealed with a thickness of 0.5 mm. Two copper plates are placed in close contact with each other, and their dimensions are 19 mm × 9 mm. Each of the copper plates is connected to a constant current power source, and the current amounts I ₁ and I ₂ (j ₁ and j _{2 in the} figure) can be individually controlled.

  Two small surface coils with a diameter of 1.3 mm and three turns are placed on the sample, and the center distance between the two coils is 6 mm. Both coils are in close contact with the sample. These were inserted into a 1 Tesla permanent magnet and irradiated with excitation pulses simultaneously with two coils, and NMR signals were simultaneously acquired.

  The coils and devices used in this example are shown in FIGS. 33 (a) to 33 (c). Fig.33 (a) is a figure which shows the small surface coil used in the present Example. FIG. 33B is a view showing a pair of polycarbonate holders used in this example. FIG. 33C shows the RF coil holder used in this example.

FIG. 34 is a diagram showing the direction of the static magnetic field H ₀ applied to the sample by the permanent magnet and the direction of the magnetic field H ₁ created by passing a current through the copper plate. If the currents I ₁ and I ₂ flow in the positive direction (the direction of the arrow in the figure) through the copper plate, the magnetic field H _{j in the} same direction as the static magnetic field H ₀ is applied to the sample, and the frequency shift amount Δω increases.

At this time, by passing the current I ₁ , a weak magnetic field is also formed around the small coil 2 at a position farther from the small coil 1, and the frequency of the small coil 2 is slightly shifted. Similarly, if the current I ₂ is supplied, a weak magnetic field is generated around the small coil 1 and the frequency is shifted. In this way, the magnetic field formed by the current can shift the frequency not only around the copper plate through which the current flows, but also in the small surface coils at remote locations. Therefore, when the coil is placed with the dimensions shown in FIG. 32, the relationship between the currents I ₁ and I ₂ and the frequency shift amount is grasped, and the frequency shift amount is measured, whereby the current I _It is necessary to verify whether ₁ and I ₂ can be calculated backward.
Therefore, acquires NMR signals by changing the current I _1, I ₂ are each independently a frequency shift amount Δω is measured whether with any dependency by the current I _1, I _2.

  The NMR signal measurement pulse sequence and the frequency shift amount calculation method used in this example were in accordance with the method of Example 1.

(Current I ₁ when current I ₂ = 0.0 A and frequency shift amount between two coils)
When the current I ₂ = 0.0 A, shows the frequency shift amount in the two coils is measured by changing the current I ₁ in increments of 0.2A in Figure 35. From this result, it can be seen that the frequency shift amount of the coil 1 is directly proportional to the current I ₁ and increases with a constant positive gradient. On the other hand, it can be seen that the frequency shift amount of the coil 2 is inversely proportional to the current I ₁ and decreases with a constant negative gradient, and the magnitude of the gradient is smaller than the gradient of the coil 1. As a result, although a frequency shift occurs even with respect to the current I ₁ located far from the coil 2, it can be said that the frequency shift amount of the coil 2 is “insensitive”.

(Current I ₁ when current I ₂ = 0.4 A and frequency shift amount between two coils)
Next, when the current I ₂ was set to 0.4 A, the frequency shift in the coils 1 and 2 was measured. FIG. 36 shows the frequency shift amount in the two coils measured by changing the current I ₁ in increments of 0.2A. From this result, the frequency shift amount of the coil 1 is almost equal to that of FIG. 35, and is directly proportional to the current I ₁ , and the gradient thereof is the same as that of FIG. 35, but in the graph, a straight line shifted downward by 0.7. It has become. That is, the absolute value of the frequency shift is a small value of about 0.7 rad / ms. On the other hand, the frequency shift amount of the coil 2 is larger than that of FIG. 35 by about 3.92 rad / ms, but is inversely proportional to the current I ₁ , the gradient is negative, and the gradient is almost equal. You can see the same thing. The frequency shift amount of the coil 2 is substantially equal to the frequency shift amount (4.02 rad / ms) of the coil 1 at the current I ₁ = 0.4 A in FIG.

From this result, it can be said that by passing the current I ₂ , the frequency shift of the coil 1 is reduced by 0.7 rad / ms, and the frequency shift amount of the coil 2 is increased by about 3.92 rad / ms. There is no other difference.

(Frequency shift amount of a current I ₁ and the two coils during the current I ₂ = -0.4A)
Next, the frequency shift in the coils 1 and 2 was measured when the current I ₂ was set to a negative value of −0.4 A. Similarly to FIG. 36, FIG. 37 shows frequency shift amounts in the two coils measured by changing the current I ₁ in increments of 0.2A.

The result is only that the vertical shift seen in FIG. 36 is reversed. It can be seen that the frequency shift of the coil 1 is increased by 0.7 rad / ms and the frequency shift amount of the coil 2 is decreased by about 3.8 rad / ms by passing the current I ₂ of −0.4 A. There is no other difference.

(Current I ₂ when current I ₁ = 0.0 A and frequency shift amount between two coils)
This time, the current I ₁ was set to zero and the current I ₂ was changed by 0.4 A step. The frequency shift amount in the two coils is shown in FIG.
The shape of the copper plate is symmetric between 1 and 2, and the positions of the coils 1 and 2 are at the same distance from the central axis of the polycarbonate cell, so the measurement result (FIG. 38) is the result of replacing coils 1 and 2 in FIG. Match.

(Current I ₂ when current I ₁ = 0.4 A and frequency shift amount between two coils)
Next, the current I _{1 was set to} 0.4 A, and the current I ₂ was changed in increments of 0.4 A for measurement. FIG. 39 shows frequency shift amounts in the two coils. This measurement result (FIG. 39) also agrees with the result of replacing coils 1 and 2 in FIG.

(Frequency shift amount of a current I ₂ and the two coils during the current I ₁ = -0.4A)
Next, the current I ₁ was set to negative −0.4 A, and the current I ₂ was changed by 0.4 A step. The frequency shift amount in the two coils is shown in FIG. This measurement result (FIG. 40) also agrees with the result of replacing coils 1 and 2 in FIG.

(Conversion method of current amount from frequency shift amount)
From the above experimental results, when multiple coils are arranged in one sample, the frequency shift amount corresponding to each region is measured, and the current distribution can be calculated backward from the frequency shift amount in each coil. I understand.
It should be noted that there is a current distribution in the measurement target, and there are two methods for converting the current amount from the frequency shift amount of the NMR signal using a plurality of small surface coils.
(I) Method of calculating by assuming that “the frequency shift amount is proportional to the amount of current in the vicinity of the coil” as the zero approximation (ii) Assuming a current distribution, the relationship between the current and the magnetic field (Bio Savart's To solve the current distribution as an "inverse problem" so that the frequency shifts at multiple locations are all consistent.

The above (i) is a method using the fact that the frequency shift amount strongly depends on the current amount near the coil from the measurement result.
Further, when solving the inverse problem in the above (ii), the value of the total current amount, for example, I ₁ + I ₂ is necessary, but this can be easily measured. According to this method, a more accurate calculation of the current distribution can be expected.

Example 4
In Example 3 described above, the current value was measured when two small coils were arranged using the spin echo method. Specifically, the current is obtained from the phase change amount (equivalent to the frequency shift amount Δω) of the echo signal at a certain time interval.

  However, the NMR signal is not limited to the echo signal, and even from the FID signal, the current can be measured by the same method.

  Therefore, in this example, it was confirmed that the current value when two small coils are arranged can be measured by the FID signal.

  Also in this example, as in Example 3, the apparatus described above with reference to FIGS. 32 and 34 was used.

In this embodiment, the current amount I ₁ is supplied only to the left copper plate in FIGS. 32 and 34, and the current is not supplied to the other right copper plate (current amount I ₂ = 0). It was. Then, the current I ₂ was set to zero, and only the current value I ₁ was changed to obtain an NMR signal (FID), and the dependence of the frequency shift amount Δω on the current I ₁ was measured.

In the NMR signal measurement pulse sequence used in this example, a rectangular wave excitation pulse having a width of 40 μs is irradiated once every 10 seconds, and the intensity of the excitation pulse is adjusted so as to excite the magnetization vector by 90 degrees. Has been.
Hereinafter, the analysis result of the FID signal acquired by the small surface coil 1 on the left side in the figure is shown.

(FID waveform and phase change amount (frequency shift amount) when current I ₁ = 0.0 A)
FIG. 42 shows an FID waveform acquired when the current I ₁ = 0.0 A. The FID at this time shows a waveform that attenuates due to the T ₂ ^* relaxation time constant. It can be seen that FID can be observed significantly until time = 20 ms on the horizontal axis.

  The phase of the FID obtained by calculating arctan (Real / Imaginary) based on FIG. 42 is shown in FIG. It can be seen from the FID up to time = 15 ms that the phase can be calculated without much dispersion.

FIG. 44 shows the time course of the FID phase (average value of five points) from 5.4 ms to 8.3 ms on the horizontal axis based on FIG. From FIG. 44, it can be seen that when the current I _{1 is} 0.0 A, the phase has a substantially constant value with respect to time.

(FID waveform and phase change amount (frequency shift amount) when current I ₁ = 0.40A)
FIG. 45 shows the FID waveform obtained when the current I ₁ = 0.40A. In the FID observed in this case, the non-uniformity of the static magnetic field becomes strong due to the current flow, and the signal is hardly visible when the horizontal axis is around time = 12 ms. Thus, compared to FIG. 42, the FID of FIG. 45 has a waveform that decays with a shorter T ₂ ^* relaxation time constant.

  FIG. 46 shows the FID phase obtained by calculating arctan (Real / Imaginary) based on FIG. As shown in FIG. 46, the phase can be calculated significantly until time = 10 ms, but it cannot be said that the phase after that has a large variance and a significant phase can be calculated. It can be seen that by applying a current, the non-uniformity of the static magnetic field increases, and the time during which the FID signal can be observed strongly is shortened.

Differences in calculating the phase change amount observed with the FID signal and the echo signal are as follows. That is, in the FID, the “observation time of the NMR signal whose phase can be calculated significantly increases / decreases depending on the amount of current” by increasing / decreasing the T ₂ ^* relaxation time constant, whereas in the case of an echo signal, it is almost constant. From the viewpoint of analyzing the obtained NMR signal, it is preferable that “the time during which the NMR signal that can analyze the phase can be observed is constant” like the echo signal.

Based on FIG. 46, FIG. 47 shows the amount of change in the phase of the FID waveform when the current I _{1 is} 0.40 A. Compared to the phase change of the current I ₁ = 0.0 A shown in FIG. 44, it can be seen that the gradient of the phase change amount is larger in FIG.

Based on FIGS. 43 and 46, the “amount of phase change during a certain time (frequency shift amount Δω)” was calculated from the lapse of time of the FID phase according to the method of Example 1. The “phase change amount at a certain time interval” calculated from the FID waveform when the current I ₁ = 0.40 A, that is, Δω was 4.17 rad / ms.

(FID waveform and phase change amount (frequency shift amount) when current I ₁ = 0.80 A)
FIG. 48 shows the FID waveform obtained when the current I ₁ is increased to 0.80 A. In the FID observed in this case, the non-uniformity of the static magnetic field is further increased by flowing a larger current, and almost no signal is visible when the horizontal axis is around time = 9 ms. Thus, the FID of FIG. 48 has a waveform that attenuates with a shorter T ₂ ^* relaxation time constant than FIG. 42 and FIG.

  Similarly to the previous method, FIG. 49 shows the FID phase obtained by calculating arctan (Real / Imaginary) based on FIG. In FIG. 49, it can be seen that the phase can be calculated significantly only up to about time = 8.5 ms. The phase after that has a large variance, and a significant phase cannot be calculated.

Based on FIG. 49, FIG. 50 shows the amount of change in the phase of the FID waveform when the current I _{1 is} 0.80 A. It can be seen that the gradient of the phase change amount is larger in FIG. 50 than the phase change amount of FIGS. 44 and 47.

Based on the time course of the FID phase in FIG. 50, the “phase change amount at a certain time interval” calculated from the FID waveform when the current I ₁ is 0.80 A, that is, Δω is 8.01 rad / ms. there were.

(FID waveform and phase change amount (frequency shift amount) when current I ₁ = −0.40 A)
Next, FIG. 51 shows the FID waveform obtained when the direction of current flow is reversed and the current I ₁ = −0.40 A. In the FID observed in this case, it can be seen that the progress of the Real and Imaginary waveforms is reversed as compared with FIG. 45 because the current flows in the reverse direction and the magnetic field direction is reversed.

  FIG. 52 shows the FID phase obtained by calculating arctan (Real / Imaginary) based on FIG. In this figure, it can be seen that the phase reverses (progresses with a negative gradient) with time.

Based on FIG. 52, FIG. 53 shows the amount of change in the phase of the FID waveform when current I ₁ = −0.40 A. It can be seen from FIG. 53 that the slope of the phase change amount is negative in FIG. 53, compared to the case where the slope of the phase change amount of current I ₁ = 0.40 A in FIG.

Based on the passage of time of the FID phase in FIG. 53, the “phase change amount at a certain time interval” calculated from the FID waveform when the current I ₁ = −0.40 A, that is, Δω is −4.19 rad / ms.

(Relationship between current I ₁ and “phase change amount (frequency shift amount) at a certain time interval”)
When the current I ₂ = 0.0 A, shows the frequency shift amount of a small surface coil 1 measured by changing the current I ₁ in increments of 0.2A in Figure 54. From this result, it can be seen that the frequency shift amount of the coil 1 is directly proportional to the current I ₁ .

Further, from the results of the present embodiment and the third embodiment, the “phase change amount at a certain time interval (frequency shift amount)” due to the current is substantially the same change amount for the FID and echo signal with respect to the current value. I understand.
Specifically, if the frequency shift amount in the coil 1 of FIG. 35 is compared with that of FIG. 54, it can be seen that the straight lines of both are substantially the same slope and the value of the intersection with the vertical axis is the same. As a result, the frequency shift amount with respect to the current is the same regardless of whether it is an FID or an echo signal, and a relational expression (calibration formula) between the current and the frequency shift amount is created by either method. If this is the case, the method can be used when calculating the current value from the frequency shift amount regardless of the method.

(Example 5)
In this example, the magnetic field formed when a current was passed through one copper plate and the frequency shift amount of the NMR signal generated thereby were analyzed. Then, it was confirmed that the frequency shift amount obtained by the analysis and the actually measured frequency shift amount were in good agreement.

(Example 5-1)
With the following method, the magnetic field formed when a current was passed through one copper plate and the frequency shift amount of the NMR signal generated thereby were analyzed. The sample was ¹ H water.

First, the analysis principle will be described.
When the current I flows through the conductor, a magnetic field H _i is formed around the conductor according to Bio-Savart's law. The magnetic field strength is proportional to the current I. This magnetic field is obtained by analysis.

In NMR measurement, a static magnetic field H ₀ is applied to a sample by a magnet. FIG. 55 is a diagram showing directions of a static magnetic field H ₀ and a magnetic field H _i described later.
Further, it is assumed that the conductor is placed in the static magnetic field, and the current I flows from left to right in FIG. Due to this current, a magnetic field H ₁ is formed around the conductor.
As a result, the magnetic field applied to the sample is the sum of the static magnetic field H ₀ by the magnet and H _i formed by the current.

Furthermore, the frequency ω [Hz] of the NMR signal is proportional to the magnetic field strength H [gauss] as shown in the following equation.
ω = γH
= Γ (H ₀ + H _i )
In the above formula, γ is the nuclear gyromagnetic ratio [Hz / gauss], and in the case of the hydrogen nucleus ¹ H, it is 4260 Hz / gauss.

The above equation, in the present embodiment, the magnetic field H _i to increase or decrease by the current I flowing in the conductors, determined as the frequency shift amount [Delta] [omega [Hz].

FIG. 56 is a perspective view showing the positions of the copper plate, the RF detection coil, and the water sample in the magnetic field analysis of this example.
In FIG. 56, the magnetic field H _i created by the current I flowing through the conductor can be calculated based on Bio-Savart's law. Specifically, when the conductor is placed in a vacuum (the permeability is 4π × 10 ⁻⁷ N / A ² ), the magnetic field H _i that the conductor creates at the position (x _p , y _p , z _p ). (X _p , y _p , z _p ) is represented by the following equation. FIG. 57 is a diagram showing a coordinate system in the following equation.

The symbols in the above formulas respectively indicate the following.
H _i : Magnetic field strength at position r [A / m] (vector)
r: position (x _p , y _p , z _p ) [m] (vector) of point P in space
r ′: position of the point Q on the coil (x _q , y _q , z _q ) [m] (vector)
I: Current [A] (scalar)
t: a unit vector representing the direction in which the current flows (the copper plate is uniformly upward in the figure) [-] (vector)

Further, when the integration of the above formula was executed, it was numerically calculated using the following approximate calculation method.
That is, assuming that the copper plate is rectangular and the current flows uniformly in the copper plate, the copper plate is divided into small elements, and it is assumed that an equally divided amount of current flows through the elements. Specifically, there is an element having a small point Q, a current flows for each element, and the elements at the plurality of points Q create a magnetic field at the point P. The magnetic field at this point P was calculated by integrating all the elements at point Q using the above formula.
In this analysis, the longitudinal direction (L direction in FIG. 57) of the copper plate was equally divided into 64, and the width direction (W direction in FIG. 57) was equally divided into 32.

Based on the above assumption, when the current I [A] flows, the z direction distribution of the magnetic field H _{x in} the x direction formed on the center of the copper plate (x _p = 0 mm, y _p = 0 mm) was analyzed.

FIG. 58 is a diagram showing an analysis result. FIG. 58 shows the results when the current I is changed to −1 [A], −0.5 [A], 0 [A], 0.5 [A], and 1 [A]. In FIG. 58, the unit of the frequency shift amount Δω on the vertical axis is [rad / ms]. Furthermore, in order to contrast with the experimental result of Example 5-2 mentioned later, 2π was multiplied by 2π and converted to rad, and s was divided by 1000 and converted to ms.
Further, the “measurement position” indicated by the arrow in FIG. 58 is the position of the water sample measured by the RF detection coil, and z _p = 0.45 mm. From FIG. 58, the distribution of the frequency shift amount Δω at this position is almost flat. It can be seen that the vicinity of the copper plate has a very steep distribution, but the distribution is almost flat just by moving slightly away from the copper plate. This flat area becomes the measurement area. The frequency shift amount Δω in this region increases / decreases depending on the magnitude of the current. By measuring this frequency shift amount Δω, the current can be calculated backward.

  FIG. 59 is a diagram showing the relationship between the frequency shift amount Δω and the current I at the position of the water sample measured by the RF detection coil. As can be seen from FIG. 59, the relationship between the two is directly proportional. It can also be seen that the current I can be easily converted from the frequency shift amount Δω.

(Example 5-2)
In this example, the amount of frequency shift was measured using a small surface coil and compared with the result of Example 5-1.

A copper plate, an RF detection coil, and a water sample (pure water) were arranged so as to have the positional relationship shown in FIG. 55, and the relationship between the current I flowing through the copper plate and the frequency shift amount Δω was measured.
In addition, as a small surface coil, a copper wire with a polyurethane film wire diameter of 50 μm was used, and this was manufactured by winding it three times in a spiral shape with an outer diameter of 1.3 mm. FIG. 60 is a diagram showing a small surface coil produced in this example.
As the NMR measurement system, a base system manufactured by MRL Technology was used with high sensitivity. As the magnet, a modified Halbach type magnetic circuit having a magnetic field strength of 1.0 Tesla and an air gap of 45 mm manufactured by NEOMAX was used.

FIG. 61 is a diagram showing the relationship between the current I [A] flowing through the copper plate and the measured frequency shift amount Δω [rad / ms]. FIG. 61 also shows the relationship (solid line) obtained from the magnetic field analysis results of FIG.
From FIG. 61, it can be seen that the measured values of the present example are in good agreement with the analysis values of Example 5-1. Therefore, the frequency shift amount Δω of the NMR signal corresponding to the current value (−1A to 1A) of the copper plate can be experimentally measured, and it can be seen that the relationship between the two is directly proportional.

(Example 6)
In this example, multipoint measurement of the frequency shift amount when the MEA was water electrolyzed was performed.

(Example 6-1)
In this example, prior to actual measurement in Example 6-2, which will be described later, the magnetic field was analyzed when the MEA was modeled with a one-dimensional equivalent circuit.

  FIG. 62 is a cross-sectional view showing a schematic configuration of the MEA used for the analysis in this example. As shown in FIG. 62, the MEA is an assembly of an electrode and a polymer electrolyte membrane, and has a structure in which a polymer electrolyte membrane (PEM) is sandwiched between upper and lower current collectors.

In the analysis of this example, the dimensions of the MEA were 23 mm × 20 mm square and the thickness was 356 μm. The current collector was a carbon mesh having a thickness of 300 μm.
One side of the polymer electrolyte membrane was electrolessly plated with Pt and Ir to form an anode side catalyst layer. Further, Pt as a catalyst was electrolessly plated on the other surface of the polymer electrolyte membrane to form a cathode side catalyst layer.
In the magnetic field analysis of this example, it was assumed that no current flows through the catalyst layer having a large electric resistance, and the current flows through the current collector.

  An RF detection coil having an inner diameter of 0.6 mm and five turns was used. There are two coil positions, x = −4.4 mm and 2.1 mm, with the center of the MEA as the origin. The distance between the coils is 6.5 mm. The measurement region in the coil depth direction is about one-fifth of the coil diameter, and is within a disk-shaped region of about 0.1 mm from the PEM surface.

  In FIG. 62, the RF detection coil is embedded on the lower side (electrolyte membrane side) of the carbon mesh and is in contact with the PEM with catalyst inside the MEA. Also, the RF detection coil is sandwiched between the upper carbon mesh and the lower carbon mesh. The magnetic field created by such two conductors is different from the case of one conductor as shown in FIG.

That is, in FIG. 62, consider a state in which the MEA is operated in the water electrolysis operation. With the anode side collector (current collector) of the MEA as the anode and the cathode side collector as the cathode, a DC voltage is applied and current I flows. The current flowing through the anode side collector electrode is I ₁ , and the current flowing through the cathode side collector electrode is I ₂ .

In this state, the current flowing through the collector electrode and the PEM was assumed as shown in FIG. That is, it was assumed that current was supplied to the left end portion of the anode-side collector electrode, and current flowed out from the anode side and the opposite end on the cathode side.
Furthermore, it was assumed that protons permeate uniformly through the PEM and have the same resistance value in all regions within the PEM plane.
Based on this assumption, the distribution of current flowing through the anode-side collector electrode and the cathode-side collector electrode is a distribution that decreases or increases both linearly with respect to the x direction. This was assumed to be an MEA equivalent circuit.

  Based on the above premise, in this embodiment, when the current I supplied from the power source is 1.2 A, the magnetic field formed in the PEM is analyzed by the method described in Embodiment 5, and the small surface coil is analyzed. The frequency shift amount of the NMR signal at the position where it was placed was calculated.

  FIG. 64 is a diagram showing the frequency shift amount Δω analyzed with respect to the positions of the cross section aa and the cross section bb shown in FIG. 63. In FIG. 64, the horizontal axis indicates the frequency shift (rad / ms), and the vertical axis indicates the position z (mm) in the thickness direction of the PEM. The coil is placed at the uppermost end, and the z position on the vertical axis is the uppermost end (Pt + Ir side) of the PEM when z = −178 μm, and the lowermost end (Pr side) when z = 178 μm.

From FIG. 64, the frequency shift amount Δω (solid line) in the z-axis direction (PEM thickness direction) at the position (x = 2.1 mm) where the RF detection coil A is placed, and the RF detection coil B are placed. The frequency shift amount Δω (broken line) in the z-axis direction at the position (x = −4.4 mm) is found.
64, the frequency shift amount at the position where the RF detection coil A is placed, that is, the frequency shift amount in the section aa (FIG. 63) is from about 6 rad / ms to about 1 rad / ms from the upper side to the lower side. It decreases to ms. In cross-section a-a, the current I ₁ flowing through the upper current electrode (at section a-a) is larger than the current I ₂ flowing through the lower collecting electrode (at section a-a) ( I 1> I 2).

On the other hand, at the position where the RF detection coil B is placed, that is, the cross-section bb (FIG. 63), on the contrary, the current I ₂ (at section bb) flowing through the lower collector electrode is the current flowing through the upper collector electrode. It is larger than I ₁ (at section bb) (I ₂ > I ₁ ). As a result, the frequency shift amount in the cross section bb is opposite in sign to the frequency shift amount in the cross section aa. Further, the frequency shift amount in the cross section bb decreases from about 0 rad / ms to about -4 rad / ms from the upper side to the lower side of the PEM.

(Example 6-2)
In this example, the frequency shift amount distribution when the MEA shown in FIG. 62 was water electrolyzed was measured and compared with the analysis result of Example 6-1.
(MEA)
An MEA was manufactured by electrolessly plating Pt and Ir on one surface (anode side) of a polymer electrolyte membrane manufactured by Asahi Glass Co., and electrolessly plating Pt on the other surface (cathode side). The dimensions of the MEA were 23 mm × 20 mm square and the thickness was 356 μm.

  As shown in FIG. 62, the obtained MEA was sandwiched between carbon meshes having a thickness of 300 μm (manufactured by Japan Gore-Tex). In addition, when sandwiching the carbon mesh and MEA, a 0.03 mm thick Pt electrode foil was also sandwiched.

The current from the power source flows from the conducting wire through the Pt electrode foil, carbon mesh, MEA, carbon mesh, Pt electrode foil, and conducting wire in this order, and returns to the power source.
The applied voltage during the water electrolysis operation was about 3 V, and the current density was 0.26 A / cm ² . The temperature of the MEA during the water electrolysis operation was about room temperature. In the present embodiment, water vapor is not supplied to the MEA.

(Small surface coil)
In this example, a NMR measuring surface coil having an inner diameter of 0.6 mm was used. A small hole was made in the carbon mesh, and the coil lead was passed through the hole to fix the coil on the carbon mesh.
FIG. 65 is a diagram showing a coil used in this example. The small surface coil was manufactured by winding a copper film having a polyurethane film diameter of 40 μm in a spiral shape with an inner diameter of 0.6 mm five times in a flat shape. This coil was manufactured by Star Engineering.
FIG. 66 is a diagram showing the coil placed on the carbon mesh in this embodiment.

  Also in this example, as in Example 6-1, the center position of the coil A was set to x = 2.1 mm, and the center position of the coil B was set to x = −4.4 mm. The origin of the position x is the center of the MEA.

(Measurement result)
The frequency shift amount was determined according to the method described in Example 1. FIG. 67 shows the frequency shift amount measured by coils A and B when the current value is 1.2A.
In FIG. 67, the frequency shift amount in the coil A is indicated by a white square (□), and the frequency shift amount in the coil B is indicated by a white triangle (Δ). Since the measurement area in the coil depth direction is about one fifth of the coil diameter, it is an area having a width of about 0.1 mm from the PEM surface. This width is shown as a bar in FIG.

In addition, from FIG. 67, the frequency shift amounts measured by the coils A and B have the same signs as the analysis results in Example 6-1. Further, similarly to Example 6-1, the frequency shift amounts measured by the coils A and B were opposite to each other, and the same relationship was obtained between the analysis value and the measurement value.
According to this example, the frequency shift amount could be measured at multiple points even in the system corresponding to the operating fuel cell. By using this method, it is possible to know the local distribution of current in the MEA of the fuel cell.

(Example 7)
(Measurement of frequency shift during water electrolysis operation)
The current measurement method by NMR was applied to MEA (Membrane Electrode Assembly) in which an electrode was joined to PEM, and the frequency shift amount of NMR signal was measured by PEM during water electrolysis operation. In order to confirm its validity, magnetic field analysis was also performed and compared with the measurement results.

(MEA equivalent circuit)
In order to confirm the validity of the measurement in comparison with the measured value, the magnetic field analysis in the MEA was performed, and the frequency shift amount of the NMR signal that increased or decreased by the magnetic field was calculated. As shown in FIG. 68, the magnetic field analysis was performed with an electrode arrangement in which current was supplied to the anode end of the MEA and current flowed from the cathode opposite end. In this analysis, protons permeate uniformly through the PEM and have the same resistance value in the entire region of the PEM, and a current flows through the electrodes on the anode side and cathode side of the PEM to form a closed circuit. I assumed that. Based on this assumption, the current I ₁ flowing through the anode electrode has a current distribution that linearly decreases with the position x, whereas the current I ₂ flowing through the cathode electrode has a current distribution that increases linearly with the position x. . The current flowing through the anode and cathode electrodes forms a magnetic field inside the PEM. The magnetic field strength distribution H _i analyzed using Biot-Savart law, was further calculates the frequency shift amount of the NMR signal from the field strength. The origin of the position x is the center of the PEM.

FIG. 69 shows the z-direction distribution of the frequency shift amount analyzed at the four sensor positions. At the position of the sensor A (x = −7.5 mm), the anode-side current I ₁ is larger than the cathode-side current I ₂ , and as a result, the frequency shift amount becomes a positive value. On the contrary, at the position of the sensor D (x = 7.5 mm), the current I ₂ on the cathode side is larger than the current I ₁ on the anode side, and the frequency shift amount in this case is a negative value opposite to that of the sensor A. It becomes. Sensors B and C located in the middle of both have an intermediate frequency shift amount.

(MEA water electrolysis operation and sensor position)
The MEA used for the water electrolysis operation was manufactured by electroless plating Pt and Ir on the anode side of the polymer electrolyte membrane and Pt on the cathode side. The dimensions of the MEA are 23 mm × 20 mm square and 356 μm thickness.

As shown in FIG. 70, the MEA is sandwiched between carbon meshes having a thickness of 300 μm as GDL (Gas Diffusion Layer), and current is supplied from the stabilized power source through the Pt electrode. In order to bring the contact resistance between GDL and MEA closer to uniform, a structure is adopted in which pressure is applied from both sides of the positive and negative electrodes using a cushioning material so that GDL and MEA are in uniform contact. The applied voltage was about 3 V and the current density was 0.26 A / cm ² .

  The surface coil for NMR measurement was obtained by winding a copper wire having an inner diameter of 0.6 mm and a wire diameter of 0.04 mm five times, and four coils were arranged between the MEA and the carbon mesh at 5 mm intervals. The surface coil wire is coated with a polyurethane coating, and is insulated from the carbon mesh. The measurement area in the coil depth direction is about one fifth of the coil diameter, and is a disk-shaped area having a depth of about 0.1 mm from the PEM surface. The representative value of the frequency of the NMR signal measured by this coil was considered to be the center of this disk, and its depth was considered to be 0.05 mm.

(Measurement result of frequency shift amount)
FIG. 71 shows the measured frequency shift amount and the x-direction distribution of the frequency shift amount obtained from the analysis. The horizontal axis of this figure is the position x, which corresponds to the position of each sensor. The vertical axis represents the frequency shift amount. A black square in the figure indicates a measured value of the frequency shift amount at the position x of the sensors A to D. The solid line shows the frequency shift amount calculated using the analysis method shown in the section (MEA equivalent circuit) and considering the thickness of the GDL. At this time, the frequency shift amount was a value at a position (z = 128 μm) inside the PEM by a distance of 0.05 mm from the anode surface position (z = 178 μm) to the measurement center of the coil.

From FIG. 71, it can be seen that the frequency shift amount gradually decreases from the sensor A to the sensor D, and the analysis value of the solid line and the measurement value of ■ are almost coincident. Further, it can be seen that the frequency shift amounts have opposite signs in A and D. From this, it can be seen that the frequency shift amount of the NMR signal corresponding to the current distribution flowing on the MEA surface can be captured.
In addition, the experimental values for the sensors C and D are slightly larger than the analytical values, but this is because the carbon mesh and the MEA are not joined with a spatially uniform contact resistance, and there is a slight bias in the current distribution. I think this is because of this.

(Example 8)
In this embodiment, a small surface coil is inserted between the GDL and the PEM in the fuel cell, and the current value when the fuel cell is water electrolyzed is measured from the NMR frequency shift amount, and the water content in the PEM is also measured. Measured. If the water electrolysis operation is performed without supplying water, the PEM is gradually dried and the current is gradually decreased. In this example, the spatial distribution of current and water content in this case was measured in time series.

  As an experiment for alternately measuring the frequency shift amount and the water content, the frequency shift amount and the water content during the water electrolysis operation were measured using the same MEA and small coil as in Example 7. FIG. 72 is a diagram showing the arrangement of MEAs and small coils in the present embodiment. As shown in FIG. 72, the small coils are inserted between the PEM and the GDL, and the number thereof is three on the anode side and one on the cathode side.

In this embodiment, the direction of the static magnetic field H ₀ is opposite to that in the seventh embodiment. When the cell was installed in the magnet, the cell direction was reversed so that the direction of the static magnetic field was reversed. Thereby, the sign of the frequency shift amount measured in the seventh embodiment is reversed. For example, the absolute value of the frequency shift amount in the case of the sensor A is the same, but the sign is negative.

The MEA was immersed in distilled water until immediately before the experiment, and the surface water was wiped off with Kimwipe immediately before the experiment to obtain an appropriate water content. The water content of MEA when treated in this way is about 10 [H ₂ O / SO ₃ ⁻ H ⁺ ] as described in Example 2. Also in this experiment, the water content is considered to be about 10 [H ₂ O / SO ₃ ⁻ H ⁺ ].

(Water electrolysis operation and measurement procedure)
The frequency shift amount was measured by the same PGSE method as in Example 7, and the water content was measured by the CPMG method. FIG. 73 is a diagram showing the measurement timings of PGSE and CPMG in the present example when the time for starting the water electrolysis operation (applying voltage) is zero.

  As shown in FIG. 73, in this example, PGSE measurement and CPMG measurement were repeated alternately. Specifically, the spin echo signal was acquired once in the PGSE measurement. In CPMG, the same measurement was performed five times to obtain an echo signal. In CPMG measurement, measurement was performed five times, and the obtained second echo signal intensity was averaged for five times to obtain a measured value. This set was repeated with one PGSE and five CPMGs as one set. TR is 5 seconds, and the time required for measurement of this one set is 30 seconds. After applying the voltage, measurement for 6 sets was performed. In CPMG measurement, 2τ = 20 ms. The time for acquiring the echo signal in one measurement was 1 second.

  Here, in order to calculate the frequency shift amount from the echo signal obtained by PGSE, the echo signal acquired before applying a voltage to the MEA is required. Therefore, in this embodiment, as shown in FIG. 73, a series of measurements was started before applying a voltage (“Off” in the figure) and used as a reference echo signal. At this time, the temperature of the magnet may rise or fall with time, the static magnetic field strength may increase or decrease, and the frequency of the NMR signal may change. In this measurement, the amount of change in the frequency was about 100 Hz in one hour. The frequency that changes in the experiment time of 150 seconds performed this time is about several Hz, which is sufficiently smaller than the frequency shift amount (about 1 kHz) that increases or decreases depending on the current. For this reason, it can be considered that the reference frequency is the same as the value (echo signal waveform) acquired before the voltage is applied. Here, the frequency shift amount was obtained with this assumption.

  In contrast to the experimental state described above, when the frequency increases or decreases with time, an NMR detection coil is installed in a place that is not affected by the magnetic field formed by the current flowing through the MEA. By measuring and using this as a reference frequency, it is possible to cancel the time change of the static magnetic field strength.

  The voltage applied to the MEA was 3.4 V at the maximum, the maximum value of the current was 1.2 A, and the DC power supply was set, and the MEA was operated in water electrolysis. FIG. 74 is a diagram showing the time change of the current flowing through the MEA. FIG. 75 is a diagram showing the change over time of the voltage applied to the MEA.

As shown in FIGS. 74 and 75, a current of 1.2 A flowed for about 10 seconds immediately after the voltage was applied to the MEA. The current density at this time was 0.25 A / cm ² . After about 10 seconds, the voltage applied to the MEA reached 3.4V, and at the same time, the current decreased to about 0.8A. After that, the current gradually dropped to about 0.5A.

  In this embodiment, PGSE measurement is performed six times at a time interval of about 30 seconds, which corresponds to the times (PGSE # 1 to # 6) indicated by arrows in FIG. Thus, the frequency shift amount was measured while the current was decreasing. On the other hand, CPMG was measured 5 times during PGSE.

(Comparison between measurement results and frequency shift obtained from magnetic field analysis)
FIG. 76 is a diagram showing the frequency shift amounts obtained by the three sensors A, C and D from the measurements at PGSE # 1 and # 4 (FIG. 74). In FIG. 76, similarly to FIG. 71 shown in the seventh embodiment, the horizontal axis represents the sensor position x and the vertical axis represents the frequency shift amount. In FIG. 76, a plot of ■ (black square) indicates the frequency shift amount measured by PGSE # 1 (current is 1.2 A). A plot of ▲ (black triangle) indicates the frequency shift amount measured by PGSE # 4 (current is 0.6 A). Further, the solid line and the alternate long and short dash line in the figure are analysis values calculated by the same magnetic field analysis as in Example 7.

  The result shown in FIG. 76 differs from the result of FIG. 71 in the sign of the frequency shift amount because the static magnetic field direction is reversed. Although the direction of the current flowing through the GDL is the same, if the direction of the static magnetic field is reversed, the sign of the frequency shift amount is reversed. If the measurer knows the direction of the static magnetic field, it will not be a problem.

  From FIG. 76, it is understood that both the measured value and the analyzed value are in good agreement with both 1.2A and 0.6A. It can be seen that if the current decreases, the amount of frequency shift decreases accordingly, which depends on the position of the sensor. In addition, since the measured value and the analyzed value coincide with each other, as assumed in the analysis, it can be inferred that in this water electrolysis experiment, a state where a current flows almost uniformly in the MEA can be achieved.

  FIG. 77 is a diagram showing a time change of the frequency shift amount obtained by the measurement from PGSE # 1 to # 6. Also in FIG. 77, measured values and analyzed values of the three sensors A, C, and D are shown. Also from this figure, the measured value and the analyzed value are in good agreement. Therefore, even when the current flowing through the MEA decreases transiently from 1.2 A to 0.6 A, it can be inferred that the state where the current flows uniformly through the MEA is maintained.

(Measurement result of water content in PEM)
Next, the result of measuring the water content in the PEM by CPMG measurement will be described.
The time change of the echo signal intensity acquired on the anode side (sensors A, C, D) is set to zero when the DC voltage is applied to the MEA, and the echo signal intensity acquired on the cathode side (sensor E) is shown in FIG. FIG. 79 shows the change with time. Here, the echo signal intensity is the intensity of the echo signal observed second using the CPMG method, and is the average signal intensity when five CPMG measurements are performed. Moreover, the value on the vertical axis is normalized by four sets of average signal intensities measured before current application.

  As shown in FIG. 80, the signal intensity increases as the water content in the PEM increases from another experiment, but the relationship between the two is not strictly a direct proportional relationship. However, in this embodiment, for the sake of simplicity, it is assumed that both are positively correlated and that the signal intensity is almost directly proportional to the water content.

  As shown in FIG. 78, when water electrolysis was started by supplying an electric current, the water content decreased in the sensor A on the anode side, and when the current was returned to zero, the original water content was restored. On the other hand, in the sensors C and D, the water content was almost constant.

  On the other hand, the water content once increased on the cathode side and then gradually decreased. As shown in FIG. 72, the sensors A and E are in substantially opposite positions.

  FIG. 81 is a diagram for explaining a phenomenon occurring in the PEM during the water electrolysis operation of the MEA. As shown in FIG. 81, water moves to the cathode side by electroosmotic flow in the PEM, and further water is decomposed by electrolysis on the anode side, so the water content on the anode side decreases. On the other hand, on the cathode side, the water content once increases due to the electroosmotic flow. However, if water electrolysis continues, the water content of the entire PEM decreases due to electrolysis, so that the water content gradually decreases with time even on the cathode side.

  In this example, a 150-second water electrolysis operation was performed, and the amount of water decomposed by this amount of current was calculated to be about several percent of the amount of water contained in the PEM. For this reason, it is considered that the increase or decrease in the water content on the anode side or the cathode side is mainly caused by the electroosmotic flow. In addition, after the water electrolysis is stopped, the water content in the PEM is considered to be a slightly reduced water content state.

  From the results of FIGS. 78 and 79 obtained here, the sensor captures the phenomenon described above, decreases on the anode side, increases once on the cathode side, then decreases, and is substantially the original after the water electrolysis is stopped. It can be said that the result returned to the same level as the water content.

In the present embodiment, the frequency shift measurement by the PGSE method and the water content measurement by the CPMG method are alternately shown. However, the frequency shift measurement and the water content measurement are simultaneously performed by a common pulse sequence. May be.
Moreover, although the example which performed the measurement of the moisture content with the frequency shift measuring apparatus was shown in the present Example, the mobility of water can also be measured with the frequency shift measuring apparatus.

Claims (14)

An apparatus for locally measuring a current at a specific portion of a sample using a nuclear magnetic resonance method,
A static magnetic field application unit that applies a static magnetic field to the sample;
A small RF coil smaller than the sample, which applies an oscillating magnetic field for excitation to the sample and acquires a nuclear magnetic resonance signal generated at a specific location of the sample;
Calculating a difference between the frequency of the nuclear magnetic resonance signal acquired by the small RF coil and the frequency of the oscillating magnetic field for excitation, and from the difference, a current calculation unit that calculates a current at the specific portion of the sample;
A measuring apparatus comprising: The measuring apparatus according to claim 1,
A detector for detecting a real part and an imaginary part of the nuclear magnetic resonance signal;
The measurement apparatus, wherein the current calculation unit calculates a difference between the frequency of the nuclear magnetic resonance signal and the frequency of the excitation oscillating magnetic field using the real part and the imaginary part detected by the detection part. The measuring apparatus according to claim 1 or 2 ,
A plurality of the small RF coils,
The plurality of small RF coils apply the oscillating magnetic field for excitation to a plurality of locations of the sample, and acquire the nuclear magnetic resonance signal,
The measurement apparatus configured to calculate the current at the plurality of locations of the sample, the current calculation unit. The measuring apparatus according to claim 1 , wherein the sample is a film. In the measuring apparatus in any one of Claims 1 thru | or 4 ,
The small RF coil applies the pulsating oscillating magnetic field and obtains an FID signal corresponding to the oscillating magnetic field for excitation,
The measurement apparatus in which the current calculation unit acquires a real part and an imaginary part of the FID signal. In the measuring apparatus in any one of Claims 1 thru | or 5 ,
Based on the nuclear magnetic resonance signal acquired by the small RF coil, a solvent amount calculation unit that calculates the amount of protic solvent in the sample;
A switching unit that switches between a first measurement mode for measuring the current of the sample and a second measurement mode for measuring the amount of the protic solvent in the sample;
Further comprising
When in the first measurement mode, the current calculation unit determines the specific location of the sample based on the difference between the frequency of the nuclear magnetic resonance signal acquired by the small RF coil and the frequency of the excitation oscillating magnetic field. Perform a current calculation,
When in the second measurement mode, the solvent amount calculation unit performs calculation of the amount of the protic solvent in the specific location in the sample based on the nuclear magnetic resonance signal acquired by the small RF coil. measuring device. The measuring apparatus according to any one of claims 1 to 6 ,
A gradient magnetic field application unit for applying a gradient magnetic field to the sample;
Based on the nuclear magnetic resonance signal acquired by the small RF coil, a mobility calculator for calculating the mobility of the protic solvent in the sample,
A switching unit that switches between a first measurement mode for measuring the current of the sample and a third measurement mode for measuring the mobility of the protic solvent in the sample;
Further comprising
In the third measurement mode,
The small RF coil applies the excitation oscillating magnetic field to the sample, and acquires a nuclear magnetic resonance signal corresponding to the excitation oscillating magnetic field and the gradient magnetic field,
The measurement apparatus in which the mobility calculation unit calculates the mobility of the specific portion of the sample based on information of the nuclear magnetic resonance signal obtained corresponding to different gradient magnetic fields. An apparatus for acquiring a current distribution in a plane of a solid polymer electrolyte membrane of a fuel cell using a nuclear magnetic resonance method,
A static magnetic field application unit that applies a static magnetic field to the solid polymer electrolyte membrane;
Applying an oscillating magnetic field for excitation to the solid polymer electrolyte membrane and acquiring a nuclear magnetic resonance signal generated at a specific location of the solid polymer electrolyte membrane, a plurality of smaller than the solid polymer electrolyte membrane, A small RF coil;
For the plurality of small RF coils, the difference between the frequency of the nuclear magnetic resonance signal acquired by the small RF coil and the frequency of the oscillating magnetic field for excitation is calculated, and the surface of the solid polymer electrolyte membrane is calculated from the difference. A current distribution acquisition unit for acquiring the current distribution in
A measuring apparatus comprising: A method for locally measuring a current at a specific portion of a sample using a nuclear magnetic resonance method,
A first step of applying an oscillating magnetic field for excitation to a specific location of the sample placed in a static magnetic field using a small RF coil smaller than the sample and acquiring a nuclear magnetic resonance signal generated at the specific location When,
Calculating the difference between the frequency of the nuclear magnetic resonance signal acquired in the first step and the frequency of the oscillating magnetic field for excitation, and from the difference, a second step of obtaining the current at the specific location of the sample;
Including a measuring method. The measurement method according to claim 9 ,
In the second step, the real part and the imaginary part of the nuclear magnetic resonance signal are detected, and the difference between the frequency of the nuclear magnetic resonance signal and the frequency of the excitation oscillating magnetic field is determined using the real part and the imaginary part. The measurement method to calculate. The measurement method according to claim 9 or 10 ,
In the first step, the small RF coil applies the pulsed oscillating magnetic field and obtains an FID signal corresponding to the exciting oscillating magnetic field,
In the second step, a real part and an imaginary part of the FID signal are detected, and a difference between the frequency of the nuclear magnetic resonance signal and the frequency of the excitation oscillating magnetic field is calculated using the real part and the imaginary part. ,Measuring method. The measurement method according to claim 9 or 10 ,
In the first step, the small RF coil is
(A) a 90 ° pulse, and
(B) Applying the excitation oscillating magnetic field in a pulse sequence including a 180 ° pulse applied after the elapse of time τ of the pulse of (a), obtaining an echo signal corresponding to the oscillating magnetic field for excitation,
In the second step, a real part and an imaginary part of the echo signal are detected, and a difference between the frequency of the nuclear magnetic resonance signal and the frequency of the excitation oscillating magnetic field is calculated using the real part and the imaginary part. ,Measuring method. The measurement method according to any one of claims 9 to 12 ,
A third step of applying an excitation oscillating magnetic field and a gradient magnetic field to a specific location of the sample, and acquiring a nuclear magnetic resonance signal generated at the specific location;
4th which calculates the mobility of the said specific location of the said sample based on the information of the nuclear magnetic resonance signal obtained by said 1st step, and the information of the nuclear magnetic resonance signal obtained by said 3rd step Steps,
Further including
In the first step and the third step, a local magnetic field is applied to the specific location of the sample using the small RF coil, and a nuclear magnetic resonance signal is acquired from the specific location,
In the first step, applying a gradient magnetic field to the sample according to a predetermined pulse sequence,
In the third step, the application of the gradient magnetic field having a magnitude different from that in the first step is performed according to a predetermined pulse sequence. In the measuring method in any one of Claims 9 thru | or 13 ,
In the first step, the small RF coil is
(A) 90 ° pulse,
(B) 180 ° pulse applied after the time τ of the pulse of (a), and (c) n 180 ° pulses applied at intervals of the time 2τ, starting after the time 2τ of the pulse of (b). Pulse (n is a natural number)
And applying the oscillating magnetic field for excitation and obtaining an FID signal corresponding to the pulse of (a) or an echo signal corresponding to the pulse of (b) or (c),
In the second step,
The frequency of the nuclear magnetic resonance signal and the oscillating magnetic field for excitation using the real part and the imaginary part of the FID signal corresponding to the pulse (a) or the echo signal corresponding to the pulse (b) or (c) While calculating the difference with the frequency of
A T ₂ relaxation time constant is calculated from the intensities of a plurality of echo signals corresponding to the pulses of (b) and (c), and from the calculated T ₂ relaxation time constant, the proticity at a specific location in the sample is calculated. A measurement method for calculating the amount of a solvent.

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