JP6006250B2 - Ion engine test equipment - Google Patents

Description

  The present invention relates to a space environment test apparatus for testing equipment used in a space environment by simulating a high vacuum and cryogenic environment substantially equivalent to the space environment. The present invention relates to an ion engine test apparatus for testing an ion engine used for attitude control of a satellite or the like.

  In general, an ion engine test apparatus is a cryostat that functions as a large-capacity pump that is cooled to 20K or less, called a cryopanel, while simulating the darkness of the universe by installing a heat absorption wall called a shroud inside the vacuum vessel A pump is installed and used at the same time as the auxiliary exhaust system. Even when the ion engine is operating, the inside of the vacuum vessel is evacuated to a high vacuum to simulate the high vacuum of the universe, and the ion engine installed in the device is tested. Is.

  In such an ion engine test apparatus, an ion engine is installed on one end side of a vacuum chamber, and a xenon ion beam ejected from the ion engine is received by a beam target installed on the other end side of the vacuum chamber. A high vacuum is maintained by condensing and exhausting the neutralized xenon gas to a cryopanel cooled to about 20K to 50K.

  In recent years, ion engines have been on the trend of higher output, and in order to cope with this, it is required to secure a large exhaust capacity of xenon gas. For this reason, in order to increase the area of the cryopanel and increase the exhaust capacity, the refrigeration capacity of the helium refrigerator that cools the cryopanel must be increased. As a result, the facility scale of the entire helium refrigerator system including incidental facilities is increased, and the installation space and cost are significantly increased.

  In order to solve such a problem, for example, Patent Document 1 discloses a helium refrigeration system in which a first cryopanel and a second cryopanel are installed so as to sandwich a beam target in a vacuum vessel and are arranged outside the vacuum vessel. An ion engine test apparatus is disclosed in which liquid helium is supplied from a machine to a first and second cryopanel via a pipe.

JP 2010-71103 A

  However, in Patent Document 1, cryopanels are provided at two locations in the vacuum vessel, and liquid helium is supplied from the helium refrigerator to the cryopanels provided at these two locations, so that the facilities are complicated. In addition, since heat is transmitted from piping for supplying liquid helium and valves provided in the middle of the piping, refrigerating capacity based on such intrusion heat is required, and the scale of the helium refrigerator is not enlarged. I do not get.

  The present invention has been made to solve such a problem, and provides an ion engine test apparatus capable of cooling a cryopanel with a simple equipment configuration without using a large helium refrigerator. It is aimed.

(1) An ion engine test apparatus according to the present invention is an ion engine test apparatus for inspecting an ion engine by injecting an ion beam from an ion engine toward a beam target installed in a vacuum chamber held at a cryogenic temperature. There,
In the space between the ion engine and the beam target, a cylindrical cryopanel provided along the inner peripheral surface of the vacuum chamber, and a direct-attached refrigerator that cools the cryopanel,
The direct-attached refrigerator has a refrigerator main body, a cylinder portion extending from the refrigerator main body, and a cold head provided at a tip of the cylinder portion, and the refrigerator main body is an outer peripheral portion of the vacuum chamber. The cylinder portion is inserted into the vacuum chamber through an opening formed in the outer peripheral portion of the vacuum chamber, and the cold head is directly attached to the cryopanel. It is.

(2) Further, in the above (1), the shroud has a double structure including an outer shroud and an inner shroud provided in a cylindrical shape along an inner peripheral wall of the vacuum chamber, and the cryopanel Is arranged to be sandwiched between the outer shroud and the inner shroud.

(3) Further, in the above-described (1) or (2), the cryopanel has a single flange portion bent on one side on both sides of the curved side, and is formed on the single flange portion. A support bar is inserted into the hole, and the support bar is inserted into a hole of a donut-shaped cover body provided on the inner peripheral surface of the vacuum chamber, so that the cryopanel is attached to the vacuum chamber. It is characterized by being.

(4) In those described above SL (3), the inner periphery of the support rod and the hole with a gap is formed between the support rod and the hole formed on one flange portion of the cryopanel The surface is in line contact.

(5) Further, in those of any one of (3) or (4), the holes of the cover of the donut shape is long elongated holes radially, and the when inserting the support rod A gap is formed between the elongated holes.

(6) Further, in the above-described one of (1) to (5), the cryopanel is formed of a plurality of curved plates, and each cryopanel is tubular along the inner wall of the vacuum chamber. And the direct-attached refrigerator is attached to each cryopanel.

  An ion engine test apparatus according to the present invention includes a cylindrical cryopanel provided along an inner peripheral surface of a vacuum chamber in a space between an ion engine and a beam target, and a direct attachment type for cooling the cryopanel. The refrigerator has a refrigerator main body, a cylinder portion extending from the refrigerator main body, and a cold head provided at a tip of the cylinder portion, the refrigerator main body Is fixed to the outer periphery of the vacuum chamber, the cylinder portion is inserted into the vacuum chamber through an opening formed in the outer periphery of the vacuum chamber, and the cold head is directly bonded to the cryopanel. Therefore, the cryopanel can be cooled with a simple equipment configuration without using a large helium refrigerator.

It is explanatory drawing of the ion engine test apparatus which concerns on one embodiment of this invention. It is a figure which shows the cross section which follows the arrow AA line in FIG. 1, Comprising: It is explanatory drawing explaining arrangement | positioning of a direct attachment refrigerator. However, the high vacuum evacuation apparatus shown in FIG. 1 is not shown. It is explanatory drawing of the cryopanel which concerns on one embodiment of this invention. It is an enlarged view which expands and shows a part of FIG. It is explanatory drawing explaining the attachment structure of a cryopanel, and the direct attachment joining structure of a direct attachment type refrigerator and a cryopanel. It is explanatory drawing of the cover body which concerns on one embodiment of this invention.

An ion engine test apparatus 1 according to the present embodiment is an apparatus for testing an ion engine 9 by injecting an ion beam toward a beam target 7 installed in a vacuum chamber 5 as shown in FIG. A cylindrical cryopanel 11 that is provided along the inner peripheral surface of the vacuum chamber 5 and is held at a cryogenic temperature, and a direct-attached refrigerator 13 that cools the cryopanel 11. Yes.
Hereinafter, each configuration and attached devices will be described in detail.

<Vacuum tank>
The vacuum chamber 5 includes a horizontal cylindrical main vacuum chamber 15 and a horizontal cylindrical sub vacuum chamber 17 connected to the end plate portion of the main vacuum chamber 15. In the following description, the terms “circumferential direction”, “axial direction”, and “radial direction” may be used in the case of indicating directions with respect to the equipment mounted in the main vacuum chamber 15. With the attached, the axial direction, the circumferential direction, and the radial direction of the cross section orthogonal to the axial direction of the main vacuum chamber 15 are referred to.

As shown in FIGS. 1 and 2, the main vacuum chamber 15 is provided with five attachment portions 19 for attaching the direct attachment type refrigerator 13 in the circumferential direction. The attachment portion 19 has a nozzle tube 19a protruding in the radial direction from an opening provided in the main vacuum chamber 15, and a nozzle flange portion 19b formed at the tip of the protruding tube (see FIG. 2).
The main vacuum chamber 15 and the sub vacuum chamber 17 are made of stainless steel, and the inner surface is subjected to a surface treatment such as buffing. The main vacuum chamber 15 and the sub vacuum chamber 17 are provided with doors and the like (not shown) for accessing the inside.
When the number of sub vacuum chambers 17 is one, the main vacuum chamber 15 and the axis line are usually installed, but a plurality of sub vacuum chambers 17 may be installed by shifting the axis line. Further, the main vacuum chamber 15 and the sub-vacuum chamber 17 may be directly connected by a flange or the like, or a partition valve or the like (not shown) may be attached between them to partition the space.

The main vacuum chamber 15 is provided with a roughing exhaust device 21 that exhausts the inside of the main vacuum chamber 15 from the atmospheric pressure to the low vacuum region, and a high vacuum exhaust device 23 that exhausts from the low vacuum region to the high vacuum region ( (See FIG. 1). These roughing evacuation device 21 and high vacuum evacuation device 23 are used to make the inside of the main vacuum chamber 15 high vacuum until the shroud 3 and the cryopanel 11 are cooled to a predetermined temperature and function as a large capacity cryopump. Used for.
Further, when the main vacuum chamber 15 and the sub-vacuum chamber 17 are partitioned and used by a partition valve (not shown), a dedicated vacuum exhaust device (not shown) may be provided so that the inside of the sub-vacuum chamber 17 can be individually evacuated. Good.

A shield plate 25 is installed inside the main vacuum chamber 15 for heat insulation. Since the shield plate 25 is usually installed to reduce the intrusion heat from the wall surface of the main vacuum chamber 15 at room temperature to the shroud 3 or the beam target 7 operated at a temperature below room temperature, the ion beam is injected. It is arranged in a place excluding a portion where an opening or an exhaust port for high vacuum exhaust is necessary. Further, the shield plate 25 is provided with an opening 25a through which the cold head 13c of the direct attachment type refrigerator 13 is inserted (see FIG. 2).
The shield plate 25 may be a stainless steel polished plate, an aluminum alloy plate, a multilayer insulation sheet called super insulation, or the like. It is good also as a structure which does not provide a shield board.

<Shroud>
The shroud 3 has a double cylindrical structure including a cylindrical outer shroud 27 and an inner shroud 29 provided in a cylindrical shape inside the outer shroud 27 with a predetermined gap. The shroud 3 is made of an aluminum alloy, but other materials may be used.
Liquid nitrogen is supplied to the shroud 3 from the liquid nitrogen supply equipment 31 and cooled.
A donut-shaped cover body 33 (described later in detail) to which cooling pipes 32 are attached is provided on both side surfaces of the cylindrical double-cylindrical shroud 3.

The outer shroud 27 is provided with an opening 27a for inserting the cold head 13c of the direct-attached refrigerator 13 (see FIG. 2).
The inner shroud 29 eliminates the viewing angle with respect to the cryopanel 11 so that the ion beam itself, sputtered particles and radiant heat generated by the beam target 7 do not directly enter the cryopanel 11 (so as not to be optically visible). In addition, chevron type (V-shaped) slats are arranged in the circumferential direction and combined into a cylindrical shape so that xenon gas can pass through. In addition, the inner shroud 29 is black, which can absorb radiant heat and effectively prevent heat from being transmitted to the cryopanel 11.
The structure of the louver and the shape and arrangement of the slats constituting the louver are not limited to those described above, and any structure that eliminates the viewing angle with respect to the cryopanel 11 and allows xenon gas to pass therethrough may be used.

In this embodiment, liquid nitrogen supplied from the liquid nitrogen supply facility 31 is used for cooling the shroud 3, but the cooling method for the shroud 3 is not limited to this, and other cooling methods may be used.
In this example, the donut-shaped cover body 33 is also cooled to the same temperature as the shroud 3. As will be described later, since the cryopanel 11 is disposed between the outer shroud 27 and the inner shroud 29, the cover body 33 is cooled, so that the effect of reducing the intrusion heat into the cryopanel 11 is increased. More preferable than not cooling.

<Beam target>
The beam target 7 is placed centered on an axial extension facing the ion engine 9. However, since the ion beam spreads radially and is ejected, it may be installed in the main body of the main vacuum chamber 15 (not shown) as necessary.
The material of the beam target 7 is aluminum, titanium, carbon or the like, but other materials can also be used.
On the back surface of the beam target 7, for temperature control, a backing plate 35 with a refrigerant channel formed of a material having high thermal conductivity such as an aluminum alloy is attached and installed outside the main vacuum chamber 15. A refrigerant is supplied from the temperature control device 37 to be cooled.
The number of pipes for supplying the refrigerant may be one for each of the supply pipes and one for the return pipes. Further, as the refrigerant, chlorofluorocarbon or the like can be used in addition to water depending on the temperature to be controlled. Further, a heat transfer sheet (not shown) or the like may be sandwiched between the beam target 7 and the backing plate 35 for the purpose of enhancing the heat transfer effect.

<Ion engine>
The ion engine 9 is installed in the sub vacuum chamber 17 using a jig (not shown), but may be installed in the main vacuum chamber 15 using a jig (not shown).

<Cryopanel>
The cryopanel 11 is formed by arranging five curved rectangular plate bodies in a cylindrical shape along the inner wall of the main vacuum chamber 15 (see FIGS. 1 and 2).
The material of the cryopanel 11 is determined by comprehensively considering thermal conductivity, emissivity, specific gravity, cost, etc. from materials that can be used in a wide temperature range from room temperature to extremely low temperature.
Further, the area of the cryopanel 11 is determined by the required exhaust speed of xenon, the refrigeration capacity of the direct-attached refrigerator 13, and the like.
In addition, since the heat capacity decreases as the thickness of the cryopanel 11 decreases, the time required for cooling to a predetermined temperature can be shortened, but the temperature distribution tends to increase. Therefore, the thickness of the cryopanel 11 is determined by appropriately adjusting the cooling station time to the predetermined temperature and the size of the temperature distribution that are in a trade-off relationship.

In the embodiment of the present invention, the material of the cryopanel 11 is a pure aluminum alloy, and a cylindrical panel is formed by dividing the panel into five in the circumferential direction. The approximate dimensions of the cryopanel 11 per sheet are as follows. The axial length is 1.9 m, the circumferential length is 1.4 m, and the thickness is 1 mm.
In the center of the cryopanel 11, a coupling portion 11a for joining the cold head 13c of the direct-attached refrigerator 13 is provided (see FIG. 3). In this example, one direct-attached refrigerator 13 is installed for each cryopanel 11.

Since the cryopanel 11 is thin and may be deformed by its own weight or the like, a plurality of ribs 11b extending in the circumferential direction are formed by drawing to prevent this, and the strength in the radial direction is improved. (See FIG. 3).
Further, angle steels 39 that function as reinforcement and attachment portions are attached to both ends of the cryopanel 11 in the axial direction. The angle steel 39 corresponds to a single flange portion of the present invention.
Two round holes 39a are provided near both ends in the circumferential direction of the angle steel 39 at both ends, and two support rods 41 are inserted in the holes 39a in the axial direction. The cryopanel 11 is installed between the outer shroud 27 and the inner shroud 29 by supporting both ends of the support rod 41 on the donut-shaped cover bodies 33 arranged on the side surfaces of both ends of the shroud 3 (FIG. 5). reference).
In this way, the cryopanel 11 is disposed between the outer shroud 27 and the inner shroud 29, and further surrounded by the donut-shaped cover body 33, thereby reducing intrusion heat from the inner side, the outer side, and the side surface. .

  The inner diameter of the hole 39a provided in the angle steel 39 at both ends of the cryopanel 11 is 10 mm, the outer diameter of the support bar 41 is 8 mm, and when the support bar 41 is inserted through the hole 39a, as shown in FIG. The outer surface of the support bar 41 and the peripheral surface of the hole 39a are in line contact in the thickness direction of the hole 39a, and the contact area is reduced. Therefore, heat conduction can be reduced, and heat input due to conduction to the cryopanel 11 is prevented.

In addition, since there is a gap between the support bar 41 and the hole 39a, the cryopanel 11 can freely move within a certain range in the axial direction, the radial direction, and the circumferential direction with respect to the support bar 41. Yes.
Further, as shown in FIG. 6, the donut-shaped cover body 33 on both side surfaces of the shroud 3 is provided with a long hole 33 a having a major axis of 17 mm × minor axis of 12 mm so as to have a major axis in the radial direction. Therefore, the support bar 41 can freely move in the axial direction, the circumferential direction, and the radial direction in a state where the support bar 41 is inserted into the elongated hole 33a, and a large amount of movement in the radial direction is particularly secured.

  Thus, by making the cryopanel 11 movable with respect to the support bar 41 and making the support bar 41 movable with respect to the cover body 33, the cryopanel 11 is fixed in a state in which the cryopanel 11 is installed. It can move freely within the range. Therefore, when the cold head 13c is directly attached to the cryopanel 11 installed in the main vacuum chamber 15, the positioning and mounting can be easily performed, and the heat accompanying the cooling of the cold head 13c, the cryopanel 11 and the shroud 3 can be easily achieved. It is possible to prevent the stress from acting on the cryopanel 11 by absorbing the deformation.

In addition, the number of the support rods 41, the outer diameter, the sizes of the holes 39a and the long holes 33a, and the like are examples of the embodiment, and are not limited to the above-described conditions.
Moreover, although this Embodiment has demonstrated about the case of the cryopanel 11 installed in the horizontal cylindrical main vacuum tank 15 whose axis is a horizontal direction, the vertical cylindrical main vacuum whose axis is a vertical direction is demonstrated. This can also be applied to the case of the tank 15 cryopanel 11. Furthermore, it goes without saying that the shape of the cryopanel 11 is not limited to a cylindrical shape, and may be other shapes.
Further, in the present embodiment, the cryopanel 11 is divided into five in the circumferential direction. However, the number of divisions is not limited to this, and when the area of the cryopanel 11 is small, it is not divided and is a single cylindrical shape. It may be.

<Direct mounting refrigerator>
The direct attachment type refrigerator 13 cools the cryopanel 11 to an extremely low temperature of about 20K to 50K. As such a direct-attached refrigerator 13, a pulse tube refrigerator or the like can be used in addition to a mechanical refrigerator such as a GM refrigerator.
As shown in FIG. 2, these direct-attached refrigerators 13 include a refrigerator main body 13a, a cylinder portion 13b extending from the refrigerator main body 13a, and a cold head 13c provided at the tip of the cylinder portion 13b. Have. Further, the refrigerator main body 13 a is formed with a flange portion 13 d for fixing the direct attachment type refrigerator 13 to the main vacuum chamber 15.
The direct refrigerator 13 inserts the cylinder portion 13b into the vacuum chamber 5 through the nozzle tube 19a from the opening formed in the outer peripheral portion of the main vacuum chamber 15, and the cold head 13c is directly connected to the cryopanel 11. The flange portion 13d is fixed to the main vacuum chamber 15 by fixing the flange portion 13d to the nozzle flange portion 19b of the main vacuum chamber 15 in the state of being attached.

In the embodiment of the present invention, the cold heads 13c of the five direct-attached refrigerators 13 are connected to the cryopanel 11 divided into five in the circumferential direction, one for each cryopanel 11 and one. ing. The cold head 13c is directly attached and joined to a coupling portion 11a provided at the center portion of the cryopanel 11, whereby the cryopanel 11 is restrained at the center portion.
In this way, by attaching the direct attachment type refrigerator 13 so as to correspond to each of the divided cryopanels 11 on a one-to-one basis by dividing the cryopanel 11, Position alignment with the vacuum chamber 15 and the cryopanel 11 can be easily performed.

  When the direct refrigerator 13 is mounted, the cylinder portion 13b of the direct refrigerator 13 is inserted into the vacuum chamber 5 through the nozzle tube 19a, and the cold head 13c is connected to the coupling portion 11a of the cryopanel 11. Directly join to. As described above, since the cryopanel 11 can freely move in the circumferential direction, the axial direction, and the radial direction, the cryopanel 11 can be moved to a desired position at the time of the direct attachment, and the direct attachment can be easily performed. it can.

In addition, after fixing the flange portion 13d of the direct-attached refrigerator 13 to the nozzle flange portion 19b, when the cold head 13c is directly attached to the coupling portion 11a of the cryopanel 11, an error due to production or assembly is absorbed. Thus, the work can be easily performed.
In particular, in the present embodiment, since the direct-attached refrigerator 13 is attached to each of the divided cryopanels 11, the degree of freedom of movement of each cryopanel 11 is high and the attachment can be made easier. .

In the ion engine test apparatus 1 configured as described above, the cryopanel 11 is cooled by the direct-attached refrigerator 13, and the intrusion heat from the pipe or the like as in the case of circulating liquid helium through the pipe. Therefore, cooling at a very low temperature can be realized with a simple structure without using a large helium refrigerator.
In this embodiment, the cryopanel 11 is attached to the main vacuum chamber 15 so as to be freely movable in the circumferential direction, the axial direction, and the radial direction. Direct attachment can be facilitated, and thermal deformation generated when the shroud 3 and the cryopanel 11 are cooled can be absorbed.

DESCRIPTION OF SYMBOLS 1 Ion engine test apparatus 3 Shroud 5 Vacuum tank 7 Beam target 9 Ion engine 11 Cryopanel 11a Coupling part 11b Rib 13 Direct attachment type refrigerator 13a Refrigerator main body 13b Cylinder part 13c Cold head 13d Flange part 15 Main vacuum tank 17 Sub Vacuum tank 19 Mounting portion 19a Nozzle tube 19b Nozzle flange portion 21 Roughing exhaust device 23 High vacuum exhaust device 25 Shield plate 25a Opening (shield plate)
27 Outer shroud 27a Opening (outer shroud)
29 inner shroud 31 liquid nitrogen supply equipment 32 cooling pipe 33 cover body 33a oblong hole 35 backing plate 37 temperature control device 39 angle steel 39a hole 41 support rod

Claims (5)

An ion engine test apparatus for testing an ion engine by injecting an ion beam from an ion engine toward a beam target installed in a vacuum chamber provided with a shroud held at a cryogenic temperature,
In the space between the ion engine and the beam target, a cylindrical cryopanel provided along the inner peripheral surface of the vacuum chamber, and a direct-attached refrigerator that cools the cryopanel,
The direct-attached refrigerator has a refrigerator main body, a cylinder portion extending from the refrigerator main body, and a cold head provided at a tip of the cylinder portion, and the refrigerator main body is an outer peripheral portion of the vacuum chamber. The cylinder portion is inserted into the vacuum chamber from an opening formed in the outer peripheral portion of the vacuum chamber, and the cold head is directly attached to the cryopanel and joined .
In addition, the cryopanel has a single flange portion bent to one side on both sides of the curved panel, and a support rod is inserted into a hole formed in the single flange portion, and the support rod is inserted into the vacuum chamber. An ion engine test apparatus , wherein the cryopanel is attached to the vacuum chamber by being inserted through a hole in a donut-shaped cover body provided on an inner peripheral surface of the ion chamber .   The shroud has a double structure including an outer shroud and an inner shroud provided in a cylindrical shape along an inner peripheral wall of the vacuum chamber, and the cryopanel is sandwiched between the outer shroud and the inner shroud. The ion engine test apparatus according to claim 1, wherein the ion engine test apparatus is arranged. Claims, characterized in that the inner peripheral surface of the bore and the support rod together with the gap is formed is in line contact between the support rod and the hole formed on one flange portion of the cryopanel Item 3. The ion engine test apparatus according to item 1 or 2 . The bore of the cover body donut shape is a long elongated holes radially, and claims 1 to 3, characterized in that a gap is formed between the slot when inserting the support rod The ion engine test apparatus according to any one of the above. The cryopanel is composed of a plurality of curved plates, each cryopanel is arranged in a cylindrical shape along the inner wall of the vacuum chamber, and the direct-attached refrigerator is attached to each cryopanel. The ion engine test apparatus according to any one of claims 1 to 4 , wherein the ion engine test apparatus is characterized.

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