JPH04191200A - Device for cooling beam target for ion engine testing device - Google Patents

Abstract

PURPOSE:To efficiently cool a beam target which is arranged in opposite to an ion engine within a vacuum container, by dividing cooling pipe lines from a refrigerator for cooling the beam target down to a low temperature, into a several groups. CONSTITUTION:A high pressure coolant main pipe 12 for feeding high pressure coolant from the body section 11 of a refrigerator 10 is connected thereto with several high pressure branch pipes 13 which are divided into a plurality of groups, and are provided therein with expansion valves 14, respectively through which they are connected cooling pipes 15 for cooling a beam target 16 in which the cooling pipes 15 are incorporated. Further, the distal ends of the cooling pipes are bundled into one pipe which is then connected to a suction pipe 17 to the refrigerator 10. Four of the cooling pipers 15 are formed so as to have lengths measured from the expansion valve 14 to the part connected to the suction pipe 7, which are equal to each other, and are arranged to cool sector shape sections of the beam target, respectively, and substantially uniformly. With this arrangement, it is possible to efficiently cool the beam target 16.

Description

[Detailed description of the invention] [Industrial application field] The present invention creates a high vacuum, extremely low temperature environment between the space environment and the roadway, and is used for attitude control of artificial satellites, etc. in space. The present invention relates to a device that cools a beam target for an ion engine test device that tests an ion engine to a low temperature.

[Conventional technology]

Ion engine test equipment generally simulates the cold darkness of space by installing a heat-absorbing wall called a shroud or shield inside a vacuum container, and also evacuates the inside of the vacuum container with a vacuum pump to create the high vacuum of space. This test simulates the ion engine installed in the equipment.

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

Furthermore, in order to house a test specimen with a large amount of released gas in the vacuum container and evacuate it to a high vacuum, it is necessary to use a very large pump to evacuate it. It was necessary to incorporate a cryogenic pumping surface, that is, a cryopanel, inside the shroud, and to cool the cryopanel to below 20°C to function as a cryopump for condensing and exhausting nitrogen, xenon, etc. residues. Conventionally, helium supplied from a helium refrigerator has been used as a cooling source for this cryopanel.

Furthermore, when the inside of the vacuum container is heated to infant temperature after the test is completed, this is generally done by introducing nitrogen scum or helium scum into the container.

Inside the vacuum chamber of the ion engine test equipment, such as
A beam target is installed to receive and stop the xenon scum that is injected as an ion beam from the ion engine. This beam target is cooled to below -50°C using a cryocooler.

The beam target is cooled as shown in Figure 2.
Usually, a cooling pipe 2 from a refrigerator 1 such as a fluorocarbon refrigerator is incorporated into a beam target 3, and the temperature after expansion through an expansion valve 4 is set to about -70°C, and the beam target 3 is
It was designed to be cooled to below 0°C.

The cooling temperature of the beam target 3 is -50°C to reduce the load on the shroud for cooling the vacuum vessel.
Furthermore, in order to reduce the load on the helium refrigerator, which is the cooling source for the cryopanel, the lower the temperature, the better, or the selection conditions were set such that the freezing temperature is the same as in a system using a normal fluorocarbon refrigerator.

[Problem to decide whether to invent or not]

However, in conventional ion engine test equipment, the beam target is small because it is usually configured to test only one engine, and the beam target is sufficiently cooled by a normal cooling method. However, in large ion engine test equipment that tests multiple engines at a time, the beam target is also large and the cooling area is large, so using normal cooling methods cannot adequately cover the beam target. There was no way to cool it down.

That is, as the piping becomes longer, the pressure loss due to the piping increases, and the evaporation temperature of the refrigerant increases, making it impossible to cool the refrigerant sufficiently. At this time, in order to lower the temperature of the refrigerant, it is possible to lower the suction pressure of the compressor to below atmospheric pressure, or if it is lowered to below atmospheric pressure, air from the atmosphere will get mixed into the piping and the refrigeration capacity will decrease. be. Furthermore, if the piping is long, the compressor oil mixed with the refrigerant may clog in the piping, making it difficult to return to the compressor and causing compressor failure.

Furthermore, in the case of a test device equipped with a plurality of ion engines as described above, if only one ion engine is used for injection, a partial heat load will be applied to the beam target, or a partial heat load will be applied to the beam target in the middle of the piping. If a heat load is generated, the refrigerant may evaporate, resulting in a large pressure loss and stopping the flow of refrigerant.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a cooling device for a beam target for an ion engine test device, which can efficiently cool a beam target used in a particularly large-sized ion engine test device.

[Means to solve the problem]

In order to achieve the above object, the beam target cooling device for ion engine test equipment of the present invention includes a refrigerator that cools the beam target placed opposite the ion engine to a low temperature inside the vacuum container. The feature is that the cooling piping is divided into multiple systems.

〔Example〕

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

First, the ion engine test device to which the present invention is applied is
Heat absorption wall (Nyuroud) and cryogenic exhaust surface inside the vacuum container,
In other words, a cryopanel is installed to create a state in which the interior of the vacuum container simulates the cold darkness of space, as described above, and a plurality of ion engines are installed at one end of the vacuum container, and a beam target is placed opposite the ion engines. This is what I did.

The beam target itself can be made of, for example, an aluminum alloy, in substantially the same way as in conventional devices.
The surface of the beam target facing the ion engine receives the xenon gas injected as an ion beam from the ion engine, and also prevents aluminum etc. sputtered by the ion beam from flying into the ion engine (back sputter). Therefore, it is formed into a lattice structure.

As shown in FIG. 1, a cooling device for cooling such a beam target to below -50° C. is constructed by connecting a high-pressure refrigerant main pipe 12 that sends high-pressure refrigerant from a main body 11 of a refrigerator 10 to four high-pressure branches. Each high-pressure branch pipe 13.13 is provided with an expansion valve 14.14 and connected to four cooling pipes 15.15 for cooling the beam target. 5 are incorporated into the beam targets 16, respectively. Further, the ends of the cooling pipes 15.15 are combined into one suction pipe 1 of the refrigerator 10.
7 is connected.

The four cooling pipes 15.15 are connected to the expansion valve 14.
．． From 14 onwards, the length up to the part connected to the suction pipe 17 is formed to have the same length, and each of them is connected to the beam target 1.
6 is divided into four approximately equally fan-shaped sections, and the piping is designed to cool one section of the section. That is, the pressure loss and 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 the compressor oil from stopping in the middle of the pipe, it is desirable that the length of the cooling pipe [5] be 20 m or less. It is preferable that the number of divisions, 16, be selected as appropriate depending on the size of the beam target]6. In this way, by setting the length of each cooling pipe 15 to 20 m or less and configuring it so that the same length causes the same pressure loss and heat load, the beam target 16
It becomes possible to sufficiently cool the entire area.

Furthermore, according to the above configuration, a fixed throttle having a predetermined diameter can be used instead of the expansion valve 14. That is, as mentioned above, the differential pressure (pressure loss) at the fixed orifice of the piping of each system can be obtained so that the refrigerant pressure in the plurality of divided systems of cooling piping becomes the same and the cooling temperature becomes uniform. By setting the diameter of the diaphragm as follows, it is possible to achieve a simple device configuration.

Incidentally, it is possible to use a refrigerator having a normal configuration, or it is usually preferable to employ a fluorocarbon refrigerator of a two-way cooling type since the refrigerator is cooled to −50° C. or lower.

C Effects of the Invention] As explained above, the beam target cooling device for an ion engine test device of the present invention divides the cooling piping of the refrigerator that cools the beam target to a low temperature into a plurality of systems. The entire soto can be efficiently and uniformly cooled to a desired low temperature state. In other words, the evaporation temperature of the refrigerant can be lowered even when the cooling area is large, and it also prevents air from getting mixed into the refrigerant, and prevents damage to the Freon compressor due to compressor oil stagnation in the refrigerant piping.
It is possible to obtain effects such as preventing an increase in pressure loss caused by evaporation of the refrigerant due to a partial heat load in the middle of the piping, and achieve economical uniform cooling of the entire beam target.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a cooling device showing an 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] 3.
High pressure branch pipe ] 4 Expansion valve ] 5... Cooling pipe
16...beam target

Claims (1)

[Claims] 1. Cooling of a beam target for an ion engine test device, characterized in that the cooling piping of a refrigerator that cools the beam target to a low temperature, which is placed inside a vacuum container facing the ion engine, is divided into a plurality of systems. Device.