JP3030657B2 - Beam target cooling system for ion engine test equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ion for forming a high vacuum and cryogenic environment substantially equivalent to a space environment and used for attitude control of an artificial satellite or the like in space. The present invention relates to a device for cooling a beam target for an ion engine test device for testing an engine to a low temperature.

[Related Art] In general, an ion engine test apparatus simulates the darkness and darkness of the universe by installing a heat absorbing wall called a shroud or a shield inside a vacuum vessel, and evacuates the inside of the vacuum vessel with a vacuum pump. To simulate the high vacuum of the universe and test the ion engine mounted on the device.

The darkness of the universe has the properties of an infinite heat absorber, and its temperature is said to be 3K. When testing a heating element such as an artificial satellite on the ground, the artificial satellite or the like is housed in the shroud, but it is almost impossible to cool the test atmosphere to 3K. For this reason, from the evaluation of thermal error, it is common to cool the shroud to 100K or less to simulate the darkness and darkness of the universe, and the cold source is mainly supplied from liquid nitrogen or helium refrigerator Helium gas has been used.

Furthermore, in order to accommodate a specimen with a large amount of released gas in the vacuum container and to evacuate it to a high vacuum, it is necessary to evacuate using a very large pump, but in such a case,
It was necessary to incorporate a cryogenic exhaust surface, that is, a cryopanel in the shroud inside the vacuum vessel, to cool the cryopanel to 20K or less, and to function as a cryopump for condensing and exhausting gases such as nitrogen and xenon. Helium supplied from a helium refrigerator is conventionally used as a cooling source for the cryopanel.

Further, when the inside of the vacuum vessel is heated to room temperature after completion of the test, it is generally performed by introducing nitrogen gas or helium gas into the shroud.

A beam target for receiving xenon gas injected as an ion beam from the ion engine is provided in a vacuum vessel of such an ion engine test apparatus. This beam target is cooled to −50 ° C. or lower by a low-temperature refrigerator.

As shown in FIG. 2, the cooling of the beam target is usually performed by a cooling pipe 2 from a refrigerator 1 such as a CFC refrigerator.
Is incorporated in the beam target 3, the temperature after expansion in the expansion valve 4 is set to about -70 ° C, and the beam target 3 is
It was designed to cool below 50 ° C.

The cooling temperature of the beam target 3 of −50 ° C. is used to reduce the load on the shroud for cooling the vacuum vessel.
Further, in order to reduce the load on the helium refrigerator, which is a cooling source of the cryopanel, the lower the temperature, the better, but it is set based on the selection condition of economical refrigeration temperature in a system using a normal CFC refrigerator.

[Problems to be solved by the invention]

However, since the conventional ion engine test apparatus is usually formed so as to test only one engine, the beam target is also small, and the cooling of the beam target by the ordinary cooling method is sufficient. However, in a large ion engine test device that tests multiple engines at once, the beam target becomes large and the cooling area becomes large, so that the beam target can be sufficiently cooled using the ordinary cooling method. I couldn't.

That is, when the pipe is long, the pressure loss due to the pipe is large, so that the evaporation temperature of the refrigerant is high and the cooling cannot be performed sufficiently. At this time, in order to lower the temperature of the refrigerant, the suction pressure of the compressor can be reduced to the atmospheric pressure or less.However, if the pressure is reduced to the atmospheric pressure or less, air from the atmosphere may be mixed into the piping and the refrigeration capacity may be reduced. . Further, if the piping is long, the compressor oil mixed in the refrigerant stops in the middle of the piping, and it is difficult to return to the compressor, which may cause a failure of the compressor.

Further, in the case of a test apparatus provided with a plurality of ion engines as described above, if only one ion engine is injected, for example, a partial heat load is applied to the beam target, or a partial When a heat load occurs, the refrigerant evaporates and the pressure loss increases, which may stop the flow of the refrigerant.

Therefore, an object of the present invention is to provide a beam target cooling device for an ion engine test device that can efficiently cool a beam target used particularly in a large ion engine test device.

[Means for solving the problem]

In order to achieve the above object, a cooling apparatus for a beam target for an ion engine test apparatus according to the present invention includes a cooling unit for cooling a beam target, which is disposed inside a vacuum vessel and opposed to an ion engine, to a low temperature. It is characterized in that the pipe is divided into a plurality of systems having the same pressure loss and arranged so that the beam target surface is cooled substantially uniformly.

〔Example〕

Hereinafter, the present invention will be described in more detail based on one embodiment shown in the drawings.

First, the ion engine test apparatus to which the present invention is applied simulates the dark and dark of the aforementioned universe in a vacuum vessel in which a heat absorbing wall (shroud) and a cryogenic exhaust surface, that is, a cryopanel, are incorporated in the vacuum vessel. In addition to the state, a plurality of ion engines are mounted on one end of the vacuum vessel, and a beam target is arranged to face the ion engine. The beam target itself can be formed of, for example, an aluminum alloy or the like, similarly to the conventional apparatus, and the surface of the beam target on the side of the ion engine receives xenon gas injected as an ion beam from the ion engine. In order to prevent aluminum or the like sputtered by the ion beam from flying to the ion engine (back spatter), a lattice structure is formed.

As shown in FIG. 1, a cooling device for cooling such a beam target to -50 ° C. or lower includes a high-pressure refrigerant main pipe 12 for sending high-pressure refrigerant from a main body 11 of a refrigerator 10 into four high-pressure branches. Into high-pressure branch pipes 13, 13
13 is provided with expansion valves 14 and 14 and connected to four cooling pipes 15 and 15 for cooling the beam targets. The cooling pipes 15 and 15 are incorporated in the beam targets 16 respectively. In addition, the ends of the cooling pipes 15 and 15 are integrated into a single
Connected to a suction pipe 17 of

The four cooling pipes 15 and 15 are formed to have the same length from the expansion valves 14 and 14 to a portion connected to the suction pipe 17 and cool the beam target surface substantially uniformly. Each of the pipes is arranged so as to cool one section of the beam target 16 divided into four fan-shaped sections substantially equally. That is, the pressure loss and the heat load in each cooling pipe 15 after the expansion valve 14 are set to be equal.

In addition, in order to make the temperature distribution of the cooling pipe uniform and to prevent compressor oil from stopping in the middle of the pipe,
Since the length of the cooling pipe 15 is desirably 20 m or less, it is preferable that the number of divisions of the beam target 16 be appropriately selected according to the size of the beam target 16. Thus, the length of each cooling pipe 15 is set to 20 m or less,
Further, by configuring the same length and the same pressure loss and heat load, the entire beam target 16 can be sufficiently cooled.

Further, according to the above configuration, a fixed throttle having a predetermined diameter can be used instead of the expansion valve 14. That is, as described above, the differential pressure (pressure loss) at the fixed throttles of the pipes of each system is obtained so that the refrigerant pressures in the plurality of divided systems of the cooling pipes are the same and the cooling temperature is uniform. By setting the aperture of such a diaphragm, a simple device configuration can be obtained.

Although a refrigerator having a normal configuration can be used, it is usually preferable to employ a CFC refrigerator of a two-way cooling type since the refrigerator is cooled to −50 ° C. or lower.

〔The invention's effect〕

As described above, the beam target cooling device for an ion engine test device of the present invention divides a cooling pipe of a refrigerator for cooling the beam target to a low temperature into a plurality of systems having the same pressure loss, and Since the beam target surface is arranged to be cooled substantially uniformly, the entire beam target can be efficiently and uniformly cooled to a desired low temperature state. That is, even when the cooling area is large, the evaporation temperature of the refrigerant can be reduced, and the prevention of air from being mixed in the refrigerant, the prevention of the failure of the CFC compressor due to the retention of compressor oil in the refrigerant piping, The effect of preventing an increase in pressure loss due to the evaporation of the refrigerant due to a partial heat load in the middle of the piping can be obtained, and the economical uniform cooling of the entire beam target can be achieved.

[Brief description of the drawings]

FIG. 1 is a system diagram of a cooling device showing one embodiment of the present invention, and FIG. 2 is a system diagram showing an example of a conventional cooling device. 10 ... refrigerator, 12 ... high-pressure refrigerant main pipe, 13 ... high-pressure branch pipe, 14 ... expansion valve, 15 ... cooling pipe, 16 ... beam target

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-258900 (JP, A) JP-A-63-20295 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B64G 7/00 B64F 1 / 26,5 / 00

Claims (1)

(57) [Claims] 1. A cooling pipe of a refrigerator for cooling a beam target, which is disposed opposite to an ion engine, to a low temperature inside a vacuum vessel, is divided into a plurality of systems having the same pressure loss, and A beam target cooling device for an ion engine test device, wherein the beam target is arranged to cool the surface substantially uniformly.