We performed a series of measurements using X-rays to assess the current performance of the Neutr... more We performed a series of measurements using X-rays to assess the current performance of the Neutron star Interior Composition Explorer (NICER) X-ray concentrators during the mission’s concept study stage. NICER will use 56 grazing-incidence X-ray concentrators in the optical system with each module focusing the incoming photons to co-aligned silicon drift detectors with 2 mm apertures. Successful X-ray timing and navigation studies require optimal signal to noise, thus by optimizing high throughput concentrators with a large collecting area we can minimize the PSF and reduce the detector aperture size, reducing background. The performance measurements were conducted in a 600 mete r X-ray beamline which collimated photons from a soft X-ray source to an X-ray CCD which was used as the detector. Several engineering test units were used to perform these studies by measuring the effective area, on and off-axis resolution, and to assess the effects of a vibration test on the module’s optical performance. We have shown that the concentrators have made significant progress towards
exceeding NICER’s final goals.
NICER 1 will use full shell aluminum foil X-ray mirrors, similar to those that are currently bein... more NICER 1 will use full shell aluminum foil X-ray mirrors, similar to those that are currently being developed for the optics to be used for the XACT 2 sounding rocket mission. Similar X-ray optics have been produced at Goddard Space Flight Center since the late 1970's. The mirror geometry used in the past and on some present missions consists of concentric quadrant shell mirrors 3 with a conical approximation to the Wolter 1 geometry. For XACT, we are developing the next generation of these optics. Two innovations introduced in the mirrors are complete shells with a curve is in the reflectors' profile to produce a sharper focus than a conical approximation. X-ray imagers, such as those of Suzaku, ASCA, GEMS, and Astro-H require two reflections. 4 Since XACT and NICER are using the optics as X-ray concentrators rather than full imaging optics, only one set of reflections is necessary. The largest shell in the NICER concentrator is 10cm diameter. Small diameter optics benefit from the rigidity of the full shell design. Also, the simplified support hardware reduced mass, which increases the effective area per unit mass. With 56 optics on NICER, each consisting of 24 full shell mirrors, an effective production process is needed for efficient manufacture of these mirrors. This production process is based on heritage techniques but modified for these new mirrors. This paper presents the production process of the innovative full shell optics and also results of optical and X-ray tests of the integrated optics. Downloaded From: https://proceedings.spiedigitallibrary.org/ on 10/16/2012 Terms of Use: https://spiedl.org/terms Proc. of SPIE Vol. 8450 845052-6 Downloaded From: https://proceedings.spiedigitallibrary.org/ on 10/16/2012 Terms of Use: https://spiedl.org/terms § Kα line is at 5.4 keV and Kβ line is at 5.9 keV ¶ The focal plane takes into consideration the length of the beam and does not assume a source at an infinite distance. The energy is measured in pulse height and converted to the correct energy in keV. Proc. of SPIE Vol. 8450 845052-7 Downloaded From: https://proceedings.spiedigitallibrary.org/ on 10/16/2012 Terms of Use: https://spiedl.org/terms
The scientific objective of the X-ray Advanced Concepts Testbed (XACT) is to measure the X-ray po... more The scientific objective of the X-ray Advanced Concepts Testbed (XACT) is to measure the X-ray polarization properties of the Crab Nebula, the Crab pulsar, and the accreting binary Her X-1. Polarimetry is a powerful tool for astrophysical investigation that has yet to be exploited in the X-ray band, where it promises unique insights into neutron stars, black holes, and other extreme-physics environments. With powerful new enabling technologies, XACT will demonstrate X-ray polarimetry as a practical and flight-ready astronomical technique. Additional technologies that XACT will bring to flight readiness will also provide new X-ray optics and calibration capabilities for NASA missions that pursue space-based X-ray spectroscopy, timing, and photometry.
The predose technique of thermoluminescence (TL) for quartz has been used extensively for retrosp... more The predose technique of thermoluminescence (TL) for quartz has been used extensively for retrospective dosimetry and archaeological authenticity testing. In this paper, we use a previously published comprehensive kinetic model for quartz, to simulate the complete sequence of experimental steps taken during the additive dose and the multiple activation versions of the predose technique. The simulation results show how both versions of the predose technique can reproduce the paleodose received by the sample with an accuracy of 1–5% in the low dose region of 0–2 Gy. For doses greater than ∼2Gy the non-linear dose dependence of the sensitivity of the “110∘C” TL peak causes significant inaccuracies in the technique. The solution of the kinetic differential equations elucidates several electron and hole processes taking place during the experimental predose procedure; these processes include the thermal transfer of holes from the Zimmerman hole reservoirs to the luminescence center, the radiation quenching of the TL sensitivity and the radiation-enhanced sensitivity of quartz samples. Specific numerical examples are given for samples exhibiting the thermal activation characteristics of “low-S0S0” and “high-S0S0” values. Quantitative results are presented for the effect of the test dose and of the calibration beta dose ββ on the accuracy of both versions of the predose technique. Results are also presented for the sensitivity of the predose technique to the natural variations of the hole concentrations in the luminescence center. Finally, the results of the predose technique simulations are compared with those from simulating the popular single aliquot SAR/OSL technique based on optically stimulated luminescence signals.
We performed a series of measurements using X-rays to assess the current performance of the Neutr... more We performed a series of measurements using X-rays to assess the current performance of the Neutron star Interior Composition Explorer (NICER) X-ray concentrators during the mission’s concept study stage. NICER will use 56 grazing-incidence X-ray concentrators in the optical system with each module focusing the incoming photons to co-aligned silicon drift detectors with 2 mm apertures. Successful X-ray timing and navigation studies require optimal signal to noise, thus by optimizing high throughput concentrators with a large collecting area we can minimize the PSF and reduce the detector aperture size, reducing background. The performance measurements were conducted in a 600 mete r X-ray beamline which collimated photons from a soft X-ray source to an X-ray CCD which was used as the detector. Several engineering test units were used to perform these studies by measuring the effective area, on and off-axis resolution, and to assess the effects of a vibration test on the module’s optical performance. We have shown that the concentrators have made significant progress towards
exceeding NICER’s final goals.
NICER 1 will use full shell aluminum foil X-ray mirrors, similar to those that are currently bein... more NICER 1 will use full shell aluminum foil X-ray mirrors, similar to those that are currently being developed for the optics to be used for the XACT 2 sounding rocket mission. Similar X-ray optics have been produced at Goddard Space Flight Center since the late 1970's. The mirror geometry used in the past and on some present missions consists of concentric quadrant shell mirrors 3 with a conical approximation to the Wolter 1 geometry. For XACT, we are developing the next generation of these optics. Two innovations introduced in the mirrors are complete shells with a curve is in the reflectors' profile to produce a sharper focus than a conical approximation. X-ray imagers, such as those of Suzaku, ASCA, GEMS, and Astro-H require two reflections. 4 Since XACT and NICER are using the optics as X-ray concentrators rather than full imaging optics, only one set of reflections is necessary. The largest shell in the NICER concentrator is 10cm diameter. Small diameter optics benefit from the rigidity of the full shell design. Also, the simplified support hardware reduced mass, which increases the effective area per unit mass. With 56 optics on NICER, each consisting of 24 full shell mirrors, an effective production process is needed for efficient manufacture of these mirrors. This production process is based on heritage techniques but modified for these new mirrors. This paper presents the production process of the innovative full shell optics and also results of optical and X-ray tests of the integrated optics. Downloaded From: https://proceedings.spiedigitallibrary.org/ on 10/16/2012 Terms of Use: https://spiedl.org/terms Proc. of SPIE Vol. 8450 845052-6 Downloaded From: https://proceedings.spiedigitallibrary.org/ on 10/16/2012 Terms of Use: https://spiedl.org/terms § Kα line is at 5.4 keV and Kβ line is at 5.9 keV ¶ The focal plane takes into consideration the length of the beam and does not assume a source at an infinite distance. The energy is measured in pulse height and converted to the correct energy in keV. Proc. of SPIE Vol. 8450 845052-7 Downloaded From: https://proceedings.spiedigitallibrary.org/ on 10/16/2012 Terms of Use: https://spiedl.org/terms
The scientific objective of the X-ray Advanced Concepts Testbed (XACT) is to measure the X-ray po... more The scientific objective of the X-ray Advanced Concepts Testbed (XACT) is to measure the X-ray polarization properties of the Crab Nebula, the Crab pulsar, and the accreting binary Her X-1. Polarimetry is a powerful tool for astrophysical investigation that has yet to be exploited in the X-ray band, where it promises unique insights into neutron stars, black holes, and other extreme-physics environments. With powerful new enabling technologies, XACT will demonstrate X-ray polarimetry as a practical and flight-ready astronomical technique. Additional technologies that XACT will bring to flight readiness will also provide new X-ray optics and calibration capabilities for NASA missions that pursue space-based X-ray spectroscopy, timing, and photometry.
The predose technique of thermoluminescence (TL) for quartz has been used extensively for retrosp... more The predose technique of thermoluminescence (TL) for quartz has been used extensively for retrospective dosimetry and archaeological authenticity testing. In this paper, we use a previously published comprehensive kinetic model for quartz, to simulate the complete sequence of experimental steps taken during the additive dose and the multiple activation versions of the predose technique. The simulation results show how both versions of the predose technique can reproduce the paleodose received by the sample with an accuracy of 1–5% in the low dose region of 0–2 Gy. For doses greater than ∼2Gy the non-linear dose dependence of the sensitivity of the “110∘C” TL peak causes significant inaccuracies in the technique. The solution of the kinetic differential equations elucidates several electron and hole processes taking place during the experimental predose procedure; these processes include the thermal transfer of holes from the Zimmerman hole reservoirs to the luminescence center, the radiation quenching of the TL sensitivity and the radiation-enhanced sensitivity of quartz samples. Specific numerical examples are given for samples exhibiting the thermal activation characteristics of “low-S0S0” and “high-S0S0” values. Quantitative results are presented for the effect of the test dose and of the calibration beta dose ββ on the accuracy of both versions of the predose technique. Results are also presented for the sensitivity of the predose technique to the natural variations of the hole concentrations in the luminescence center. Finally, the results of the predose technique simulations are compared with those from simulating the popular single aliquot SAR/OSL technique based on optically stimulated luminescence signals.
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Papers by Erin R Balsamo
exceeding NICER’s final goals.
exceeding NICER’s final goals.