JPH0668419B2 - Cryogenic refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention includes a pre-cooling refrigeration circuit for expanding a refrigerant gas such as helium gas and a JT circuit (Joule Thomson circuit).
A cryogenic refrigerator having an original circuit, in which a cryogenic temperature is generated in a cryogenic part in a cryostat (a cryogenic tank) and a cryogenic operating device is operated by the cryogenic temperature, in particular,
The present invention relates to measures for low-frequency vibration during operation of low-temperature operating equipment.

(Prior Art) Conventionally, as a cryogenic refrigerator of this type, helium gas is used as a refrigerant, and high-pressure helium gas compressed by a compressor is expanded by an expander to radiate a low temperature generation part in a cryostat from the outside. The pre-cooling refrigeration circuit to be shielded and the compressed helium gas discharged from the separately installed compressor are pre-cooled in the pre-cooling refrigeration circuit, and the pre-cooled helium gas is further expanded by the JT valve in Joule-Thomson expansion to expand it. A helium refrigerator provided with a JT circuit for generating an extremely low temperature in the low temperature generating portion of the cryostat by the action is well known.

By the way, in such a helium refrigerator, a GM cycle (Gifford-McMahon cycle), an improved Solvay cycle, etc. are usually adopted as the refrigeration cycle of the pre-cooling refrigeration circuit. It is inevitable that vibration will occur due to gas flow due to switching between high / low pressure, collision between displacer and cylinder, or expansion / contraction of cylinder due to switching between high / low pressure.
It was difficult to apply it to photodetection sensors used in spectroscopic research, which dislikes extremely small vibrations on the order of m.

Therefore, conventionally, when operating such a light detection sensor, the operation of the entire refrigerator is stopped each time, and the heat capacity of the sensor unit and the heat station is used to determine that the temperature at the sensor unit is the temperature required for cooling. It is done so that the measurement is completed by the time it rises over.

(Problems to be Solved by the Invention) However, when the operation of the entire refrigerator is stopped during the operation of the sensor in this way, the following problems occur.

That is, when the refrigerator is operating, the supply pressure of helium gas is
The return pressure is maintained at about 20 atm and the return pressure is maintained at about 1 atm, and the helium gas after passing through the JT valve is partially liquefied and maintained at a cryogenic temperature of about 4K. However, if the operation of the refrigerator is stopped from this state, at the same time, J-T
The pressure in the circuit is balanced at about 8 atm, and as shown in FIG. 3, the helium liquid in the sensor portion instantly reaches the supercritical pressure and its temperature rises to 5.5 to 8K.

Further, in general, when the temperature becomes extremely low, the specific heat is small, so that the heat capacity of each part becomes small, and it is unavoidable that the temperature rises sharply when there is a slight heat load.

Therefore, the temperature of a sensor that uses the superconducting phenomenon or a sensor that reduces low thermal noise rises rapidly, and as a result, the superconducting phenomenon is broken or thermal noise increases, making measurement difficult. It causes problems such as

The present invention has been made in view of the above points, and an object thereof is to provide a cryogenic refrigerator such as a helium refrigerator having a binary circuit including the pre-cooling refrigeration circuit and the JT circuit described above. On the other hand, when the low temperature operating equipment such as the light detection sensor is operating, the operation of the pre-cooling refrigeration circuit including the expander which is the vibration source is stopped, while the operation of the JT circuit for cooling the low temperature operating equipment in the cryostat is performed. Continue,
Then, by adjusting the return pressure of the refrigerant in the JT circuit to a pressure equivalent to the temperature required for cooling the low-temperature operating device, the time for holding the low-temperature sensor at an extremely low temperature can be greatly extended, It is to be able to perform the measurement stably.

(Means for Solving Problems) In order to achieve this object, a solution means of the present invention is, as shown in FIG. 1, a low temperature operation device (S) operated at an extremely low temperature.
A cryostat (C) having a low temperature generation part (C ₁ ) for cooling and holding the refrigerant, and a precooling refrigeration circuit for expanding the refrigerant gas compressed by the compressor (2) by the expander (6) to generate an extremely low temperature. (1) and the high-pressure refrigerant gas from the compressor (23) are pre-cooled by the pre-cooling refrigeration circuit (1), and the pre-cooled refrigerant gas is subjected to Joule-Thomson expansion to cause a low temperature generation part (C) of the cryostat (C). ₁ ) The target is a helium refrigerator equipped with a JT circuit (20) for generating a cryogenic temperature.

And as its characteristic, the bypass means (53) for bypassing the refrigerant gas in the high pressure side pipe (29) of the JT circuit (20) to the low pressure side pipe (37), and the high pressure side pipe (29).
Pressure adjusting means (54) for reducing the pressure of the refrigerant gas inside to the refrigerant gas pressure (for example, 1 atm) inside the low-pressure pipe (37).
To provide.

Further, when the low-temperature operation device (S) is operating, the control of stopping the operation of the pre-cooling refrigeration circuit (1) and operating both the bypass means (53) and the pressure adjusting means (54) A means (55) is provided.

(Operation) With the above configuration, in the present invention, when the low temperature operating device (S) is not operated and is cooled and maintained at an extremely low temperature,
Both the pre-cooling refrigeration circuit (1) and the JT circuit (20) are operated. At this time, neither the bypass means (53) nor the pressure adjusting means (54) in the JT circuit (20) operate, and the high pressure refrigerant gas from the compressor (23) does not flow in the JT inside the cryostat (C). The valve (36) expands the Joule-Thomson to generate a cryogenic temperature in the low temperature generating portion (C ₁ ), and the cryogenic temperature cools the low temperature operating device (S).

On the other hand, when operating the low temperature operating device (S), the operation of the compressor (2) and the expander (6) of the precooling refrigeration circuit (1) is stopped by the control of the control means (55), and the precooling is performed. The entire refrigeration circuit (1) is shut down. On the other hand, the operation of the JT circuit (20) is continued, and at that time, the bypass means (53) and the pressure adjusting means (54).
Both work. And both means (53), (54)
The refrigerant gas discharged from the compressor (23) flows from the middle of the high pressure side pipe (29) to the low pressure side pipe (37) by the bypass means (53) along with the operation of the pressure adjusting means (54). ), The pressure of the refrigerant gas in the low-pressure side pipe (37) is adjusted to be reduced, and then the pressure is returned to the compressor (23). Therefore, in this case, the operation of the expander (6) of the pre-cooling refrigeration circuit (1) is stopped, so that the low-temperature operating device (S) does not generate vibrations that it dislikes, and the operation can be reliably performed. .

Moreover, since the return pressure of the refrigerant is adjusted to the gas pressure in the low-pressure side pipe (37), the refrigerant pressure in the low-temperature operating device section will be maintained at an appropriate pressure, and the rapid temperature rise will occur. Therefore, it is possible to maintain the operating device section at an extremely low temperature for a long time and stabilize the measurement operation of the low temperature operating device (S).

(Example) Hereinafter, the Example of this invention is described based on drawing.

FIG. 1 shows the overall configuration of a helium refrigerator of a two-stage two-stage compression cycle according to an embodiment of the present invention, and (C) is a photodetection sensor (S) for spectroscopic studies as a low-temperature operating device operated at an extremely low temperature. ) Has a low temperature generating part (C ₁ ) for keeping it in a cooled state, (1) is a JT circuit (2
In (0), a pre-cooling refrigeration circuit having an improved solve gas cycle for compressing and expanding helium gas to pre-cool it, (20) compresses helium gas to generate cryogenic temperature and expands the Joule-Thomson JT The pre-cooling refrigeration circuit (1) extends across the pre-cooling compressor unit (A) and the cryostat (C), and the JT circuit (20) includes a JT side compressor unit (B). ) And the cryostat (C) are provided in parallel with each other.

The pre-cooling compressor unit (A) separates the pre-cooling compressor (2) for compressing helium gas and the lubricating oil for the compressor (2) from the high-pressure helium gas compressed by the compressor (2). The adsorber (4) is provided with an oil separator (3) for removing and an adsorber (4) for adsorbing and removing impurities such as water and impure gas in the helium gas that has passed through the oil separator (3). Is connected to the high pressure side inlet (7a) of the casing (7) in the expander (6) fitted in the cryostat (C) via the high pressure side pipe (5).

The expander (6) has a casing (7) arranged outside the cryostat (C) and a cylinder (8) connected to a lower portion of the casing (7). A second heat station (10) and a first heat station (9), which are inserted into the low temperature generating portion (C ₁ ) of the cryostat (C), are provided on the outer circumference. Although not shown, a rotary valve that opens in the casing (7) each time it rotates and supplies the helium gas flowing from the high pressure side inlet (7a) into the cylinder (8), A valve motor for driving the rotary valve is fitted in the cylinder (8),
A slack piston that reciprocates according to opening and closing of the rotary valve, and a displacer that is integrally engaged with the slack piston to reciprocate in the cylinder (8) to expand the helium gas by Simon are inserted. . The first heat station (9) of the cylinder (8) has a radiation shield portion (C ₂ ) arranged so as to surround the low temperature generation portion (C ₁ ) in the cryostat (C).
Is in thermal contact with the expander (6), the high pressure helium gas is expanded in the cylinder (8) by opening the rotary valve in the expander (6) to generate a low temperature state. And the radiation shield part (C ₂ ) which is held by the second heat stations (9) and (10) and is in thermal contact with the first heat station (9).
Is cooled to a low temperature, and the low temperature generation part (C ₁ ) inside is cooled from the outside.

Further, the casing (7) of the expander (6) is opened with a low pressure side outlet (7b) for discharging the expanded low pressure helium gas, and the low pressure side outlet (7b) is connected to the low pressure side pipe (11). Is connected to the surge bottle (12) provided in the precooling compressor unit (A) through the surge bottle (12), which is connected to the suction side of the precooling compressor (2). The pressure fluctuation of the low-pressure helium gas discharged from 6) is absorbed by the surge bottle (12) and sucked into the compressor (2). As described above, the high-pressure helium gas discharged from the precooling compressor (2) is supplied to the expander (6) via the oil separator (3) and the adsorber (4), and the expander (6) is supplied. The temperature of the heat stations (9), (10) is lowered by adiabatic expansion at the temperature to shield the low temperature generation part (C ₁ ) in the cryostat (C) from radiation and to be described later in the JT circuit (20). The precoolers (31) and (33) are precooled, and the expanded low pressure helium gas is returned to the compressor (2) via the surge bottle (12) and recompressed.

On the other hand, in the JT side compressor unit (B), a low-stage compressor (21) that compresses helium gas to a predetermined pressure, and a compressor (21) from high-pressure helium gas discharged from the compressor (21) ( 21) an oil separator (22) for separating and removing lubricating oil, a high-stage compressor (23) for further compressing the high-pressure helium gas passing through the oil separator (22) to a higher pressure, and the compressor ( An oil separator (24) that separates and removes the lubricating oil for the compressor (23) from the high-pressure helium gas discharged from (23), and the impurities in the high-pressure helium gas that have passed through the oil separator (24) are removed by adsorption. And an adsorber (25) for

In addition, the cryostat (C) has a primary side and a secondary side.
First to third JT heat exchangers (26) to (28) for exchanging heat with each other between the helium gases passing through the secondary sides.
Of the JT heat exchangers (26) to (28), the second and third JT heat exchangers (27) and (28) are the radiation shield parts (C) of the cryostat (C). ₂ ) is located inside. The primary side of the first J-T heat exchanger (26) is connected to the adsorber (25) of the J-T side compressor unit (B) via a high pressure side pipe (29). The primary sides of the first and second JT heat exchangers (26) and (27) are connected to the adsorber (30) and the outer periphery of the first heat station (7) of the expander (6). Connected to the first precooler (31) disposed in the second and third J-T
Similarly, the primary sides of the heat exchangers (27) and (28) are the second heat station (8) of the adsorber (32) and the expander (6).
It is connected via a second precooler (33) arranged on the outer circumference. Further, the primary side of the third J-T heat exchanger (28) is supported by the lower end of the cylinder (8) of the expander (6) and is located in the low temperature generating part (C ₁ ) in the cooler (34). On the other hand, it is connected via an adsorber (35) and a JT valve (36) for expanding Joule-Thomson of high-pressure helium gas. The cooler (34) includes the third and second J-T heat exchangers (2
The first J-T heat exchanger (26) through each secondary side of 8) and (27)
Connected to the secondary side of the first J-T heat exchanger (26), and the secondary side of the first J-T heat exchanger (26) is connected to the low-stage compressor (B) of the J-T side compressor unit (B) via the low-pressure side pipe (37). It is connected to the suction side of 21). Therefore, the two compressors (21) and (23) connected in series in two stages compress the helium gas to a high pressure and supply the helium gas to the cryostat (C) side. Third JT heat exchanger (2
In 6) to (28), heat is exchanged with the low temperature and low pressure helium gas returning to the JT side compressor unit (B), and
After the first and second precoolers (31) and (33) heat-exchange the first and second heat stations (9) and (10) of the expander (6) to cool them, the JT valve (36) ) Is used to expand the Joule-Thomson, and the cooler (34) produces 1 atm of helium at about 4K.
To the third J-T heat exchanger (26) to (28) through the secondary side of each, the low-stage compressor (21) of the J-T side compressor unit (B)
It is configured to be inhaled and recompressed.

The two compressors (2) of the compressor unit (A) for the pre-cooling compressor (A) and the compressor unit (B) for the JT side (2)
The structure of 1) and (23) and its peripheral devices are constructed in the same structure. In the figure, (40) is each compressor (2), (2
Oil separators (3), (22), (2) from the discharge side of 1), (23)
With a discharge gas coil installed in the middle of the flow path leading to 4),
This discharge gas coil (40) is for each compressor (2), (21),
It is wound around the upper half of the outer circumference of the casing (23) (not shown). In addition, each compressor (2), (2
A cooling water coil (41) through which cooling water flows is wound around the entire outer peripheral surface of the casings 1) and (23) substantially parallel to the discharge gas coil (40). Thereby, the high temperature and high pressure helium gas discharged from the compressors (2), (21) and (23) and flowing in the discharge gas coil (40) is cooled.

Further, (42) is an oil coil wound around the lower half of the outer peripheral surface of the casing of each compressor (2), (21), (23) substantially parallel to the cooling water coil (41). Coil (42)
Of the compressor (2), (21), (23) has an oil reservoir at the bottom of the casing, and a downstream end of the compressor (2) via an injection pipe (44) provided with an orifice (43). ), (21), (23) respectively connected to the suction side, and the lubricating oil in the casing discharged from the compressor (2), (21), (23) together with the helium gas is transferred to the oil coil (42). And is cooled by the cooling water in the cooling water coil (41) and then injected into the suction helium gas by the orifice (43) of the injection pipe (44).

Further, (45) is a connecting pipe for connecting the discharge side of the oil separator (22) and the discharge side of the adsorber (25) of the JT side compressor unit (B), and in the middle of the connecting pipe. A high pressure control valve (46) for controlling the pressure of the helium gas discharged from (B), a gas ballast tank (47) for storing the high pressure helium gas flowing out from the high pressure control valve (46), and the tank ( An intermediate pressure control valve (48) for controlling the discharge pressure of the low stage compressor (21) by supplying the high pressure helium gas in 47) to the discharge side of the oil separator (22) is provided.

As a feature of the present invention, the high-pressure side pipe (29) is provided in the middle of the high-pressure side pipe (29) in the JT circuit (20).
A first solenoid valve (50) for opening and closing is provided. Also,
One end of a bypass pipe (51) is branched and connected to the high-pressure pipe (29) immediately upstream of the first solenoid valve (50), and the other end of the bypass pipe (51) is the low-pressure pipe (37). Connected to the
In the middle of the bypass pipe (51), the bypass pipe (5
A second solenoid valve (52) for opening and closing 1) is provided. The first solenoid valve (50) is closed to close the high pressure side pipe (29) and the second solenoid valve (52) is opened. By bypassing the valve to open the bypass pipe (51), the helium gas in the high pressure side pipe (29) is bypassed to the low pressure side pipe (37) through the bypass pipe (51), thereby forming a bypass means (53). ing.

In addition, the bypass pipe (5
The pressure of the high-pressure helium gas in the high-pressure side pipe (29) during the operation of the bypass means (53) is set in the low-pressure side pipe (3).
The helium gas pressure in 7), in other words, the electromagnetic constant pressure adjusting valve (54) as a pressure adjusting means for reducing the pressure to the pressure (1 atm) corresponding to the required cooling temperature (for example, 4K) of the light detection sensor (S). Is provided.

And the compressor (2) in the said pre-cooling refrigeration circuit (1)
And expander (6), both compressors (21), (23) in JT circuit (20), first and second solenoid valves (50), (5
2) and the constant pressure regulating valve (54) are controlled by the control device (55). That is, when the photodetection sensor (S) is activated (measured) by the control device (55),
The compressor (2) and the expander (6) in the pre-cooling refrigeration circuit (1) are deactivated to stop the operation of the pre-cooling refrigeration circuit (1) itself, and the bypass means (53) and the constant pressure regulating valve (54). (Pressure adjusting means) is operated to reduce the helium gas in the high pressure side pipe (29) to a predetermined pressure by the constant pressure adjusting valve (54) and return it to the low pressure side pipe (37).

Further, in the JT circuit (20), a liquid reservoir (56) for storing helium liquid is arranged in the pipe between the JT valve (36) and the cooler (34) for sensor cooling. It is set up.

Next, the operation of the helium refrigerator of the above embodiment will be described.

When the light detection sensor (S) in the cryostat (C) is not operating, the first solenoid valve (5) in the bypass means (53) is
0) is opened, while the second solenoid valve (52) is closed to enter a normal state. In this normal state, the light detection sensor (S)
Is cooled.

To explain this action in detail, the two compressors (21) of the pre-cooling refrigeration circuit (1), the compressor (2) and the JT circuit (20),
(23) When is started and the refrigerator enters the steady operation state,
The high-pressure helium gas supplied from the compressor (2) is expanded by the expander (6) on the cryostat (C) side in the pre-cooling refrigeration circuit (1), and each heat of the cylinder (8) is expanded with the expansion of this gas. The temperature of the radiation shield part (C ₂ ) that is in thermal contact with the stations (9), (10) and the first heat station (9) decreases, and the low temperature generation part (C ₁ ) in the cryostat (C) becomes Radiation shield to the outside.

Meanwhile, at the same time, from the cryostat (C) to J-
Helium gas returning through the T circuit (20) is sucked and compressed by the low-stage compressor (21) and cooled by the cooling water coil (41) around it to room temperature 300K, and this helium gas is separated into oil. After the oil component is separated in the vessel (22), it is sucked and compressed in the high-stage compressor (23). Further, the gas discharged from the compressor (23) is cooled to a room temperature of 300 K by the cooling water in the cooling water coil (41) around the compressor (23), separated by the oil separator (24), and then adsorbed. Impurities are adsorbed at (25), and the clean high-pressure helium gas thus obtained is supplied to the cryostat (C).

The high-pressure helium gas supplied to the cryostat (C) side enters the primary side of the first J-T heat exchanger (26), and J-T
Returning to the T side compressor unit (B), it is heat-exchanged with the low pressure helium gas on the secondary side and cooled from room temperature 300K to about 70K,
After that, the first which is cooled to 50-60K of the expander (6)
It enters the first precooler (31) around the heat station (9) and is cooled to about 55K. This cooled gas is the 2nd J
After entering the primary side of the −T heat exchanger (27) and returning to the JT side compressor unit (B), after being cooled to approximately 20K by heat exchange with the low pressure helium gas on the secondary side, the expander 15 of (6)
Second heat station (10) cooled to ~ 20K
It enters the second precooler (33) on the outer circumference and is cooled to about 15K. Furthermore, the gas enters the primary side of the 3rd J-T heat exchanger (28) and cools to about 5K by heat exchange with the low-pressure helium gas on the secondary side to the J-T side compressor unit (B). Is
Reach the JT valve (36). The J-T valve (36) throttles the high-pressure helium gas and expands it by Joule-Thomson to 1 atm,
It becomes helium in a 4.2K gas-liquid mixed state and is supplied to the cooler (34). Then, in this cooler (34), the latent heat of vaporization of the liquid portion of the helium in the gas-liquid mixed state is used for cooling the light detection sensor (S) as the cooled object or for liquefying or recondensing other helium gas. .

Then, from the cooler (34) to the third J-T heat exchanger (2
The low-pressure helium gas returning to the secondary side of 8) becomes saturated gas of about 4.2K, and the second and first J-T heat exchangers (27), (2
In 6), the high pressure helium gas on the primary side was cooled to about 3
After temperature rises to 00K, JT side compressor unit (B)
Return to. After that, the same cycle is repeated and the freezing operation is performed.

On the other hand, when the light detection sensor (S) is operated to perform measurement, the control device (55) operates to operate the compressor (2) and the expander (6) in the pre-cooling refrigeration circuit (1).
Are stopped together, and the operation of the pre-cooling refrigeration circuit (1) itself is stopped. Due to this operation stop, vibration of the expander (6) does not occur, and vibration to the light detection sensor (S) can be reduced as much as possible.

Further, at the same time when the operation of the pre-cooling refrigeration circuit (1) is stopped, the first solenoid valve (50) is closed, while the second solenoid valve (5) is closed.
2) is opened. By switching the opening and closing of both solenoid valves (50) and (52), the JT valve (36) is discharged from the compressor (23) of the JT circuit (20) and passes through the high pressure side pipe (29). ,
The flow of helium gas to the cooler (34) is blocked, and the high-pressure helium gas in the high-pressure side pipe (29) is bypassed to the low-pressure side pipe (37) through the bypass pipe (51). The pressure of the helium gas in the low pressure side pipe (37) is reduced by the valve (54). Therefore, the helium pressure in the cooler (34) for cooling the light detection sensor (S) is maintained at a predetermined pressure as in the cooling operation, and a rapid temperature rise of the cooler (34) is avoided. Therefore, it is possible to keep the light detection sensor (S) in a cryogenic state and continue its measurement operation for a long time.

Further, since the liquid reservoir (56) is arranged in the pipe between the J-T valve (36) and the cooler (34), the latent heat of the helium liquid can be effectively used, and the light detection sensor (S It is possible to suppress the temperature rise of 1) for a longer time.

FIG. 3 shows the sensor unit (cooler (34)) after the operation of the pre-cooling refrigeration circuit (1) is stopped in the configuration of the above embodiment.
FIG. 3 shows the degree of temperature rise in the conventional example (the one in which the operation of the JT circuit (20) itself is stopped), and according to FIG. In comparison, it can be seen that the cryogenic temperature can be maintained for a longer time.

In the above embodiment, the constant pressure adjusting valve (54) was used as the pressure adjusting means for reducing the helium gas bypassed from the high pressure side pipe (29) to the low pressure side pipe (37) to a predetermined pressure. A control valve may be used.

Further, the present invention can be applied not only to the helium refrigerator of the compression cycle as in the above embodiment, but also to helium refrigerators having other types of binary circuits, and further cryogenic refrigeration using a refrigerant other than helium. Can be applied to the machine.

(Effects of the Invention) As described above, according to the present invention, a JT circuit that expands a high-pressure refrigerant gas by Joule-Thomson to generate cryogenic temperature in a cryostat for cooling and holding a low-temperature operating device is provided. For a cryogenic refrigerator having a dual circuit with a pre-cooling refrigeration circuit for pre-cooling the refrigerant gas of the J-T circuit, the operation of the pre-cooling refrigerating circuit is stopped and the J-T By reducing the pressure of the refrigerant gas in the high-pressure side pipe of the circuit to the pressure of the refrigerant gas in the low-pressure side pipe and bypassing it to the low pressure side, the operation is performed while eliminating the occurrence of vibration accompanying the operation of the pre-cooling refrigeration circuit. It is possible to suppress the pressure rise of the refrigerant gas in the equipment part and eliminate its sudden temperature rise, and therefore even low temperature operating equipment that is sensitive to vibration can be kept at cryogenic temperature for a long time, Measurement work It is possible to stabilize the movement.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and FIG. 2 show an embodiment of the present invention, FIG. 1 is an overall configuration diagram of a helium refrigerator, and FIG. 2 is a temperature at a sensor portion when a light detection sensor is operating. It is a characteristic view which shows a rising characteristic.
FIG. 3 is a Mollier diagram of the gas cycle in the pre-cooling refrigeration circuit and JT circuit of the helium refrigerator. (1) ... pre-cooling refrigeration circuit, (2) ... pre-cooling compressor,
(6) ... expander, (9), (10) ... heat station, (20) ... JT circuit, (21) ... low-stage compressor,
(23) …… High-stage compressor, (26) to (28) …… JT heat exchanger, (29) …… High-pressure side piping, (31), (33) …… Precooler, (34) …… Cooler, (36) …… JT valve, (37)…
… Low-pressure side piping, (50) …… first solenoid valve, (51) …… bipie piping, (52) …… second solenoid valve, (53) …… bypass means, (54) …… constant pressure regulating valve, (55) …… Control device,
(56) …… Liquid reservoir, (C) …… Cryostat, (C ₁ )
...... Low temperature generation part, (C ₂ ) ...... Radiation shield part, (S) ...
… Light detection sensor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoichi Tanetani 1304 Kanaoka-machi, Sakai City, Osaka Daikin Industries, Ltd.Kanaoka Plant, Sakai Manufacturing Co., Ltd. (72) Kazuo Miura, 1304 Kanaoka-machi, Sakai, Osaka Prefecture Daikin Industries, Ltd. Sakai Plant Kanaoka Plant (72) Inventor Tadashi Ogura 1304 Kanaoka Town, Sakai City, Osaka Daikin Industries, Ltd.Sakai Plant Kanaoka Plant (72) Satoshi Noguchi 1304 Kanaoka Town, Sakai City, Osaka Sakai Plant, Daikin Industries, Ltd. Kanaoka Factory (56) Reference JP 61-235650 (JP, A) JP 61-79953 (JP, A)

Claims (1)

[Claims] _1. A cryostat (C) having a low temperature generating portion (C ₁ ) for cooling and holding a low temperature operating device (S) which operates at an extremely low temperature, and a refrigerant gas compressed by a compressor (2) is expanded. A pre-cooling refrigeration circuit (1) that expands at a machine (6) to generate cryogenic temperature, and a high-pressure refrigerant gas from the compressor (23) are pre-cooled by the pre-cooling refrigeration circuit (1), and the pre-cooled refrigerant gas is A cryogenic refrigerator equipped with a JT circuit (20) for expanding a Joule Thomson to generate a cryogenic temperature in a low temperature generating portion (C ₁ ) of the cryostat (C), the JT circuit ( Bypass means (53) for bypassing the refrigerant gas in the high pressure side pipe (29) of the 20) to the low pressure side pipe (37)
A pressure adjusting means (54) for reducing the pressure of the refrigerant gas in the high-pressure side pipe (29) to the pressure of the refrigerant gas in the low-pressure side pipe (37), and during operation of the low temperature operating device (S), A cryogenic temperature characterized by comprising: a control means (56) for controlling the bypass means (53) and the pressure adjusting means (54) so as to stop the operation of the pre-cooling refrigeration circuit (1). refrigerator.