Dilution refrigerator unit

Abstract

The application provides a dilution refrigerator unit, and particularly relates to the field of desktop ultra-low temperature refrigeration equipment. The dilution refrigerator unit comprises a first vacuum device, a second vacuum device, a liquid nitrogen cold trap and a front-stage refrigerator. The inner cavity of the first vacuum device is provided with a radiation-proof screen. The inner cavity of the radiation-proof screen is provided with an adsorption device. The liquid nitrogen cold trap is arranged inside the adsorption device. The liquid nitrogen cold trap is externally provided with a heating element. The front-stage refrigerator is arranged on the top of the second vacuum device. A primary cold head of the front-stage refrigerator extends into the inner cavity of the second vacuum device. The first vacuum device and the second vacuum device are connected through a bellows. The primary cold head is connected with the inner cavity of the radiation-proof screen through a gas-gap type thermal switch. The application makes full use of the surplus cold capacity of the primary cold head, and builds a low-temperature heat exchange environment for the liquid nitrogen cold trap without interfering with the normal cooling and circulation conditions of the dilution refrigerator unit, so that the evaporation of liquid nitrogen is effectively inhibited, the loss of liquid nitrogen is reduced, and the liquid supplement frequency is reduced.

Description

Technical Field

[0001] This invention patent relates to the field of desktop cryogenic refrigeration equipment, specifically to a dilution refrigeration unit. Background Technology

[0002] In common desktop dilution refrigeration systems, the purity of the working gas is crucial. During operation, the purity of the working gas and the stability of the throttling components directly affect the refrigeration performance and long-term operational stability of the system. If the working gas is impure, it can easily cause pipe blockage in extremely low-temperature environments, and may even lead to refrigeration cycle failure. Therefore, a cold trap is often required in the dilution refrigeration system to maximize the purification of the working gas.

[0003] However, existing liquid nitrogen cold traps require regular manual replenishment of liquid nitrogen to maintain their low temperature. If the liquid nitrogen is insufficient, the temperature inside the cold trap will rise, impurities will not be fully adsorbed, and abnormal temperatures will result. In addition, traditional cold traps continuously consume and evaporate liquid nitrogen, resulting in high operating costs. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides a desktop dilution refrigeration unit, the specific technical solution of which is as follows: A dilution refrigeration unit includes a first vacuum device, a second vacuum device, a liquid nitrogen cold trap, and a pre-cooling unit; the first vacuum device has a radiation shield inside its cavity; the radiation shield has an adsorption device inside its cavity; the liquid nitrogen cold trap is located inside the adsorption device; a heating element is located outside the liquid nitrogen cold trap; the pre-cooling unit is located on top of the second vacuum device; the first-stage cold head of the pre-cooling unit extends into the cavity of the second vacuum device; the first vacuum device and the second vacuum device are connected by a bellows; the first-stage cold head is thermally connected to the radiation shield via an air gap thermal switch.

[0005] Preferably, the top of the first vacuum device is provided with an air inlet pipe communicating with the air inlet of the liquid nitrogen cold trap, and an air outlet pipe communicating with the air outlet of the liquid nitrogen cold trap.

[0006] Preferably, the inlet side of the air intake pipe is connected to the pre-treatment gas processing device.

[0007] Preferably, the outlet side of the gas outlet pipe is connected to the gas return purification device.

[0008] Preferably, the heating element is an electric heater or a wound heating wire.

[0009] Preferably, the outer surface of the radiation shield is covered with radiation shielding material.

[0010] Preferably, the inner cavity of the adsorption device is filled with liquid nitrogen.

[0011] More preferably, the cooling temperature of the first-stage cold head is 50K.

[0012] The beneficial effects of this invention are: 1. This invention can make full use of the surplus cooling capacity of the first-stage cold head of the pre-cooling unit, and build a stable low-temperature heat exchange environment for the built-in liquid nitrogen cold trap without interfering with the normal cooling and circulation conditions of the dilution refrigeration unit. By circulating helium in the pre-cooling pipeline, the heat exchange temperature difference is reduced, effectively inhibiting liquid nitrogen evaporation, reducing liquid nitrogen loss, extending the liquid nitrogen replenishment cycle, and reducing the frequency of daily equipment maintenance and the overall operating cost of the machine. 2. This invention is equipped with a radiation shield wrapped with radiation-proof material to minimize heat loss from external radiation. 3. The present invention has a heating element installed outside the liquid nitrogen cold trap. When the dilution refrigeration unit stops running, the liquid nitrogen cold trap can be heated and impurities inside can be discharged without the need for an external heater. The operation is simple and the stability is higher. Attached Figure Description

[0013] The accompanying drawings constituting this invention are provided to further understand this application and do not constitute an undue limitation of this application.

[0014] Figure 1 This is a schematic diagram of the overall structure of the present invention; In the diagram, 1-first vacuum device; 2-radiation shield; 3-adsorption device; 4-liquid nitrogen cold trap; 401-heating element; 5-inlet pipe; 6-outlet pipe; 7-second vacuum device; 8-pre-stage refrigerator; 801-first stage cold head; 9-bellows; 10-air gap thermal switch. Detailed Implementation

[0015] The specific implementation of a dilution refrigeration unit provided by the present invention will be further described in conjunction with the accompanying drawings and embodiments.

[0016] like Figure 1 As shown, a dilution refrigeration unit includes a first vacuum device 1, a liquid nitrogen cold trap 4, a second vacuum device 7, and a pre-cooling unit 8. The first vacuum device 1 has a radiation shield 2 installed inside its cavity; the radiation shield 2 has an adsorption device 3 installed inside its cavity; the liquid nitrogen cold trap 4 is located inside the adsorption device 3; the pre-cooling unit 8 is located on top of the second vacuum device 7; and the first-stage cold head 801 of the pre-cooling unit 8 extends downwards into the cavity of the second vacuum device 7.

[0017] Preferably, the inner cavity of the adsorption device 3 is filled with liquid nitrogen.

[0018] Preferably, in order to achieve the regeneration and desorption of the liquid nitrogen cold trap 4 and remove the captured impurities (water vapor, pump oil vapor, high boiling point impurities), a heating element 401 is provided on the outside of the liquid nitrogen cold trap 4; the heating element 401 includes, but is not limited to, an electric heater or a wound heating wire.

[0019] Preferably, the first vacuum device 1 and the second vacuum device 7 are connected by a bellows 9.

[0020] Preferably, the primary cold head 801 achieves on / off thermal coupling with the radiation shield 2 through an air gap thermal switch 10.

[0021] Preferably, the top of the first vacuum device 1 is provided with an air inlet pipe 5 that communicates with the air inlet of the liquid nitrogen cold trap 4, and an air outlet pipe 6 that communicates with the air outlet of the liquid nitrogen cold trap 4.

[0022] It is worth noting that the inlet side of the inlet pipe 5 is connected to the pre-treatment gas processing device (not shown in the figure); the outlet side of the outlet pipe 6 is connected to the return gas purification device (not shown in the figure). Specifically, the ³He / 4 He mixed working gas enters the inlet side of the liquid nitrogen cold trap 4 built into the first vacuum device 1 through the inlet pipe 5. After impurity removal and pre-cooling, it is connected downwards to the low-temperature end for heat absorption and cooling. The ³He gas phase extracted from the distillation chamber flows into the liquid nitrogen cold trap 4 along the internal pipeline for cold gas recovery and secondary impurity collection. Finally, it enters the external return gas purification device from the outlet pipe 6. The ³He / 4 The mixed working gas is sent back to the pre-treatment gas device and connected to the inlet pipe 6 to flow back into the liquid nitrogen cold trap 4, completing the closed-loop full cycle.

[0023] To reduce heat loss due to external radiation, the outer surface of the radiation shield 2 is also covered with radiation shielding material (not shown in the figure).

[0024] More preferably, the cooling temperature of the first-stage cold head 801 is about 50K, which fully reaches the working range of liquid nitrogen (the boiling point of nitrogen at normal pressure is 77K).

[0025] During use, when the dilution refrigeration unit needs to perform operations such as eliminating hot spots and charging mixed working gas, the air gap thermal switch 10 is turned on, and the first-stage cold head 801 continuously provides cooling to the liquid nitrogen cold trap 4, keeping the temperature of the radiation shield 2 at around 50K. This ensures that the adsorption device 3 inside the radiation shield 2 receives as little external radiative heat leakage as possible. When the gas passes through the liquid nitrogen cold trap 4, the 50K low temperature inside the radiation shield 2 effectively reduces the evaporation of liquid nitrogen. When charging ³He / 4When the mixing of the working gas is completed, the air gap thermal switch 10 is disconnected, thereby reducing the heat load on the first-stage cold head 801. When the dilution refrigeration unit stops working, the heating element 401 is opened according to the regeneration desorption and impurity removal requirements to remove impurities from the liquid nitrogen cold trap 4. The liquid nitrogen cold trap 4 can be heated directly without the need for an external heater (such as a hot air gun), which is simple to operate and highly stable.

[0026] This invention provides a desktop dilution refrigeration unit that makes full use of the surplus cooling capacity of the first-stage cold head. Without interfering with the normal cooling and circulation of the dilution refrigeration unit, it creates a low-temperature heat exchange environment for the liquid nitrogen cold trap, effectively suppressing liquid nitrogen evaporation, reducing liquid nitrogen loss and replenishment frequency.

[0027] In this invention, terms such as "upper," "lower," "bottom," and "top" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are merely used to facilitate the description of the structural relationships of the various components or elements of this invention and do not specifically refer to any particular component or element in this invention, nor should they be construed as limiting the invention. Terms such as "connected" and "linked" should be interpreted broadly, indicating a fixed connection, an integral connection, or a detachable connection; a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can determine the specific meaning of the above terms in this invention based on the specific circumstances, and they should not be construed as limiting the invention.

[0028] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A dilution refrigeration unit, characterized in that, It includes a first vacuum device, a second vacuum device, a liquid nitrogen cold trap, and a pre-cooling unit; The first vacuum device has a radiation shield inside its cavity; the radiation shield has an adsorption device inside its cavity; the liquid nitrogen cold trap is located inside the adsorption device; and a heating element is located outside the liquid nitrogen cold trap. The pre-cooling unit is located at the top of the second vacuum device; the first-stage cold head of the pre-cooling unit extends into the inner cavity of the second vacuum device. The first vacuum device and the second vacuum device are connected by a bellows; the first-stage cold head is thermally connected to the radiation shield via an air gap thermal switch.

2. The dilution refrigeration unit according to claim 1, characterized in that, The first vacuum device is provided with an air inlet pipe that communicates with the air inlet of the liquid nitrogen cold trap and an air outlet pipe that communicates with the air outlet of the liquid nitrogen cold trap.

3. The dilution refrigeration unit according to claim 2, characterized in that, The inlet side of the air intake pipe is connected to the pre-treatment gas processing device.

4. The dilution refrigeration unit according to claim 2, characterized in that, The outlet side of the gas outlet pipe is connected to the gas return purification device.

5. The dilution refrigeration unit according to claim 1, characterized in that, The heating element is an electric heater or a wound heating wire.

6. The dilution refrigeration unit according to claim 1, characterized in that, The outer surface of the radiation shield is covered with radiation-proof material.

7. The dilution refrigeration unit according to claim 1, characterized in that, The inner cavity of the adsorption device is filled with liquid nitrogen.

8. The dilution refrigeration unit according to claim 1, characterized in that, The cooling temperature of the first-stage cold head is 50K.

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