Multi-constant-temperature-stage adiabatic demagnetization refrigerator

Abstract

The application provides a multi-constant-temperature-stage type adiabatic demagnetization refrigerator, which comprises a heat sink, an ADR body, a thermal switch and a thermal load. The ADR body comprises multiple stages of ADRs, and the thermal switch comprises multiple thermal switches. The multiple stages of ADRs and the thermal load are connected through reasonable design of the thermal switches, the timing cooperation between the multiple stages of ADRs in series is realized, the operation timing between the multiple stages of ADRs is adjusted, multi-constant-temperature continuous refrigeration is provided for different thermal loads, and the structure is simple and compact.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of extremely low-temperature refrigeration, and particularly relates to a multi-constant-temperature-stage adiabatic demagnetization refrigerator. BACKGROUND

[0002] With the development of frontier scientific fields such as space measurement and quantum technology, the demand for extremely low-temperature refrigeration is increasing. The working temperature range of a detector for space observation is usually required to be lower than 100 mK to realize high-resolution and high-sensitivity measurement; in order to reduce noise in the system and improve the signal-to-noise ratio so as to observe weak signals, some gravitational wave detectors also require to work at 100 mK. As one of the earliest extremely low-temperature refrigeration technologies, adiabatic demagnetization refrigeration (ADR) has the advantages of high efficiency, compactness, independence from gravity conditions and scarce resources 3 , and has become the most promising extremely low-temperature refrigeration technology for space applications.

[0003] ADR is based on the magnetic heat effect of paramagnetic materials with changes in the external magnetic field, and the basic components include paramagnetic salt pills, a magnet, a thermal switch, a heat sink and a cold head. An ideal ADR performs a reverse Carnot cycle between the heat sink temperature T high and the refrigeration temperature T low via four processes of isothermal magnetization, adiabatic demagnetization, isothermal demagnetization and adiabatic magnetization. After the magnetic heat material is pre-cooled to the heat sink temperature T high , the thermal switch between the heat sink and the paramagnetic salt pills is closed, the salt pills are isothermally magnetized, the magnetization heat is released to the heat sink, and the target upper limit of the magnetic field is reached; the thermal switch between the heat sink and the paramagnetic salt pills is opened, the salt pills are adiabatically demagnetized and cooled to the refrigeration temperature T low ; in the case of a heat load, the demagnetization rate is controlled, the salt pills are isothermally demagnetized and cold energy is generated to maintain the heat load temperature constant; when the magnetic field temperature is reduced to the target lower limit of the magnetic field, the thermal switch is kept open, the salt pills are magnetically regenerated under adiabatic conditions, and the temperature is raised to the heat sink temperature T high , and the above cycle is repeated.

[0004] With the increase of space cryogenic refrigeration power, the traditional ADR is limited by the magnetic field strength and the size of the refrigeration system, and it is difficult to meet the requirement of maintaining large refrigeration power for a long time. Through the series structure of constant temperature stage and the parallel structure of alternating operation, continuous adiabatic demagnetization refrigeration CADR can be realized. In space observation and other applications, different working temperatures are required for the detector and the working circuit, and single constant temperature stage CADR can only provide continuous refrigeration at one temperature for the heat load, which is difficult to meet the demand of continuous refrigeration at multiple refrigeration temperatures. At present, the common multi-constant temperature stage CADR system needs to set multiple constant temperature stages ADR for different heat loads. Taking the CADR system connecting two heat loads as an example, four stages of ADR are generally required, including two constant temperature stages ADR, and the structure is complex. SUMMARY

[0005] Therefore, it is necessary to provide a multi-constant temperature stage adiabatic demagnetization refrigerator with compact structure for the complex structure of the prior art.

[0006] To solve the above problems, the technical scheme adopted by the present application is as follows:

[0007] The present application provides a multi-constant temperature stage adiabatic demagnetization refrigerator, which comprises a heat sink, an ADR body, a thermal switch and a heat load, the ADR body comprises a first stage ADR 1, a second stage ADR 2 and a third stage ADR 3, the thermal switch comprises a first thermal switch HS1, a second thermal switch HS2, a third thermal switch HS3 and a fourth thermal switch HS4, and the heat load comprises a first heat load and a second heat load, wherein:

[0008] The two ends of the first thermal switch HS1 are connected with the heat sink and the first stage ADR 1 respectively, the two ends of the second thermal switch HS2 are connected with the first stage ADR 1 and the first heat load respectively, the two ends of the third thermal switch HS3 are connected with the second stage ADR 2 and the first heat load respectively, the second thermal switch HS2 and the third thermal switch HS3 are connected between the first stage ADR 1 and the second stage ADR 2, the fourth thermal switch HS4 is connected between the second stage ADR 2 and the third stage ADR 3, and the other end of the fourth stage ADR 4 is connected with the second heat load.

[0009] In some embodiments, each stage of ADR body contains paramagnetic salt pills (11) and superconducting magnets (12) surrounding the paramagnetic salt pills (11).

[0010] In some embodiments, the paramagnetic salt pills are gadolinium gallium garnet or chrome potassium alum or gadolinium lithium fluoride or iron ammonium alum or ytterbium gallium garnet, and the superconducting magnets are niobium titanium or niobium tin.

[0011] In some embodiments, the thermal switch comprises an air gap thermal switch or a superconducting thermal switch or a magnetoresistive thermal switch or a mechanical thermal switch.

[0012] The application has the beneficial effects as follows:

[0013] The multi-constant-temperature-stage adiabatic demagnetization refrigerator provided by the application comprises a heat sink, an ADR body, a thermal switch and a thermal load, the ADR body comprises multiple-stage ADRs, the thermal switch comprises multiple thermal switches, the multiple-stage ADRs and the thermal load are connected by reasonably designing the thermal switches, the timing cooperation between the multiple-stage ADRs is realized, the operation timing between the multiple-stage ADRs is adjusted, multi-constant-temperature continuous refrigeration is provided for different thermal loads, and the structure is simple and compact. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments of the application or the prior art description. Obviously, the drawings described below are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0015] Figure 1 The structure schematic diagram of the multi-constant-temperature-stage adiabatic demagnetization refrigerator provided by the embodiments of the application is shown.

[0016] Figure 2 The operation timing of the three-stage-temperature-stage adiabatic demagnetization refrigerator provided by the embodiments of the application is shown. DETAILED DESCRIPTION

[0017] The embodiments of the application will be described in detail below, and examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the application, and cannot be understood as a limitation of the application.

[0018] In the description of the application, it should be understood that the terms "upper", "lower", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the application.

[0019] In addition, the terms "first", "second", "third", "fourth", "fifth", "sixth", "seventh" and "eighth" are only used for descriptive purpose and cannot be understood as indicating or implying relative importance or implying the number of the technical features indicated. Therefore, the features defined with "first", "second", "third", "fourth", "fifth", "sixth", "seventh" and "eighth" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0020] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and embodiments.

[0021] Please refer to Figure 1 The structure schematic diagram of the multi-constant-temperature-stage adiabatic demagnetization refrigerator provided by the embodiments of the present application includes a heat sink 1, an ADR body, a thermal switch and a thermal load. The ADR body includes a first-stage ADR 1, a second-stage ADR 2 and a third-stage ADR 3. The thermal switch includes a first thermal switch HS1, a second thermal switch HS2, a third thermal switch HS3 and a fourth thermal switch HS4. The thermal load includes a first thermal load 6 and a second thermal load 7. The connection relationship of each component and the implementation mode thereof are described in detail below.

[0022] It should be noted that the multi-constant-temperature-stage adiabatic demagnetization refrigerator provided by the embodiments of the present application has a three-stage ADR, such as the first-stage ADR 1, the second-stage ADR 2 and the third-stage ADR 3 in the figure. The thermal switch includes the first thermal switch HS1, the second thermal switch HS2, the third thermal switch HS3 and the fourth thermal switch HS4 (respectively as the reference numerals 2-5 in the figure). However, in practice, it is not limited to the three-stage CADR structure, and other multi-constant-temperature-stage CADR (two-stage, four-stage, five-stage) are also within the protection scope of the present application. Figure 1

[0023] In the present embodiment, the two ends of the first thermal switch HS1 are connected with the heat sink and the first-stage ADR 1 respectively. The two ends of the second thermal switch HS2 are connected with the first-stage ADR 1 and the first thermal load respectively. The two ends of the third thermal switch HS3 are connected with the second-stage ADR 2 and the first thermal load respectively. The second thermal switch HS2 and the third thermal switch HS3 are connected between the first-stage ADR 1 and the second-stage ADR 2. The fourth thermal switch HS4 is connected between the second-stage ADR 2 and the third-stage ADR 3. The other end of the fourth-stage ADR 4 is connected with the second thermal load.

[0024] ​It can be understood that the first thermal switch HS1 is responsible for connecting the heat sink 1 and the first stage ADR1; the second thermal switch HS2 is responsible for connecting the first stage ADR1 and the first heat load 6; the third thermal switch HS3 is responsible for connecting the second stage ADR2 and the first heat load 6, the second thermal switch HS2 and the third thermal switch HS3 are jointly connected with the first stage ADR1 and the second stage ADR2; the fourth thermal switch HS4 is responsible for connecting the second stage ADR2 and the third stage ADR3. By reasonably designing the thermal switch to connect each stage of ADR and heat load, each stage of ADR relays refrigeration, and the timing cooperation between each stage of the multi-stage series ADR is realized.

[0025] In the embodiment, each stage of ADR body contains a paramagnetic salt pill (11) and a superconducting magnet (12) surrounding the paramagnetic salt pill (11). The paramagnetic salt pill is gadolinium gallium garnet or chromium potassium alum or gadolinium lithium fluoride or iron ammonium alum or ytterbium gallium garnet, and the superconducting magnet is niobium titanium or niobium tin.

[0026] Further, the temperature of the heat sink 1 is 4K, the temperature of the first heat load 6 is 1K, the temperature of the second heat load 7 is 0.25K, and the temperature difference between the cold head and the load is ignored. The salt pill of the first stage ADR1 is gadolinium gallium garnet (GGG), the superconducting magnet coil material is niobium titanium, the upper limit magnetic field strength applied is 4T, the heat release temperature of the first stage ADR1 is 4K, the refrigeration temperature is 1K, and the first stage ADR1 is responsible for providing cold to the second stage ADR2 and maintaining the temperature of the first heat load 6 constant. The salt pill of the second stage ADR2 is chromium potassium alum (CPA), the superconducting magnet applies an upper limit magnetic field strength of 2T, the heat release temperature of the second stage ADR2 is 1.2K, and the refrigeration temperature is 1K, 0.2K in turn, and the second stage ADR2 is responsible for providing cold to the third stage ADR3 and maintaining the temperature of the second heat load 6 constant. The salt pill of the third stage ADR3 is chromium potassium alum CPA, the superconducting magnet applies an upper limit magnetic field strength of 1T, the third stage ADR3 is a constant temperature stage, the refrigeration temperature is 0.25K, and the temperature of the heat load 7 is maintained constant. The salt pill is chromium potassium alum CPA, and the superconducting magnet applies an upper limit magnetic field strength of 1T.

[0027] Further, the selection of the thermal switch between each stage is not limited to the air gap type thermal switch, the superconducting type thermal switch. The magnetoresistance thermal switch and the mechanical thermal switch are all suitable for the protection scope of the present patent.

[0028] For simplicity of description, all thermal switches are considered as ideal thermal switches, and the response time of the thermal switch is ignored, as shown in Figure 2 Taking a three-stage CDR system with a single cycle length of 90min as an example, its working process is as follows:

[0029] (1) First refrigeration

[0030] In the ideal state, without considering the connection between the CADR system and the heat load, close all heat switches, the entire CADR system is pre-cooled to about 4K by the heat sink and kept stable, then disconnect HS1, close HS2, HS3, HS4, the first stage ADR1 carries out demagnetization refrigeration, cools the second stage ADR2 and the third stage ADR3 to about 1K; disconnect HS2, close HS1, HS3, HS4, the first stage ADR1 carries out magnetization regeneration, the second stage ADR2 carries out demagnetization refrigeration, cools the third stage ADR3 to about 0.2K; thus each stage ADR is cooled to the vicinity of the working temperature, open the constant temperature control, enter the periodic continuous refrigeration working cycle.

[0031] (2) Periodic continuous refrigeration

[0032] In 0-t1 time, HS1, HS3 is disconnected, HS2, HS4 is closed, the first stage ADR1 carries out isothermal demagnetization at 1K, maintains the temperature of the heat load 6 constant at 1K; the second stage ADR2 carries out isothermal demagnetization at 0.2K, absorbs the magnetization heat of ADR3; the third stage ADR3 carries out isothermal magnetization at 0.25K, releases magnetization heat to ADR2, maintains the temperature of the heat load 7 constant at 0.25K.

[0033] In t1-t2 time, HS1, HS3, HS4 is disconnected, HS2 is closed, the first stage ADR1 continues to carry out isothermal demagnetization at 1K, maintains the temperature of the heat load 6 constant; the second stage ADR2 carries out adiabatic magnetization, the temperature rises from 0.2K to 1.2K; the third stage ADR3 continues to carry out isothermal demagnetization at 0.25K, maintains the temperature of the heat load 7 constant.

[0034] In t2-t3 time, HS1, HS4 is disconnected, HS2, HS3 is closed, the first stage ADR1 continues to carry out isothermal demagnetization at 1K, maintains the temperature of the heat load 6 constant, and absorbs the magnetization heat of ADR2; the second stage ADR2 carries out isothermal magnetization at 1.2K, releases magnetization heat to ADR1; the third stage ADR3 continues to carry out isothermal demagnetization at 0.25K, maintains the temperature of the heat load 7 constant.

[0035] In t3-t4 time, HS1, HS3, HS4 is disconnected, HS2 is closed, the first stage ADR1 continues to carry out isothermal demagnetization at 1K, maintains the temperature of the heat load 6 constant; the second stage ADR2 carries out adiabatic demagnetization, the temperature drops from 1.2K to 0.2K; the third stage ADR3 continues to carry out isothermal demagnetization at 0.25K, maintains the temperature of the heat load 7 constant.

[0036] During the time interval t4 to t5, HS1, HS2, and HS4 are disconnected, while HS3 is closed. The first-stage ADR1 undergoes adiabatic magnetization, with the temperature rising from 1K to 4K. The second-stage ADR2 undergoes isothermal demagnetization at 1K, maintaining the temperature of heat load 6 at a constant 1K. The third-stage ADR3 continues isothermal demagnetization at 0.25K, maintaining the temperature of heat load 7 at a constant temperature.

[0037] During the time interval t5 to t6, HS2 and HS4 are disconnected, while HS1 and HS3 are closed. The first-stage ADR1 is isothermally magnetized at 4K, releasing magnetization heat to the heat sink. The second-stage ADR2 continues isothermally demagnetizing at 1K, maintaining the temperature of heat load 6 constant. The third-stage ADR3 continues isothermally demagnetizing at 0.25K, maintaining the temperature of heat load 7 constant.

[0038] During the time interval t6 to t7, HS1, HS2, and HS4 are disconnected, and HS3 is closed. The first-stage ADR1 performs adiabatic demagnetization, and the temperature drops from 4K to 1K. The second-stage ADR2 continues to perform isothermal demagnetization at 1K to maintain the temperature of heat load 6 constant. The third-stage ADR3 continues to perform isothermal demagnetization at 0.25K to maintain the temperature of heat load 7 constant.

[0039] During the time interval t7 to t8, HS1, HS3, and HS4 are disconnected, while HS2 is closed. The first-stage ADR1 isothermally demagnetizes at 1K, maintaining the temperature of heat load 6 at a constant 1K. The second-stage ADR2 performs adiabatic demagnetization, with the temperature decreasing from 1K to 0.2K. The third-stage ADR3 continues isothermally demagnetizing at 0.25K, maintaining the temperature of heat load 7 at a constant temperature.

[0040] Within the time interval t8 to 90 minutes, HS1 and HS3 are disconnected, while HS2 and HS4 are closed. The first-stage ADR1 continues isothermal demagnetization at 1 K, maintaining a constant temperature for heat load 6. The second-stage ADR2 isothermal demagnetizes at 0.2 K, absorbing the magnetization heat from ADR3. The third-stage ADR3 isothermal magnetizes at 0.25 K, releasing the magnetization heat to ADR2, maintaining a constant temperature for heat load 7 at 0.25 K. This completes one full continuous refrigeration cycle.

[0041] It should be noted that the timing design of the second-stage ADR2 given in the above embodiment is only one of the operating modes. In actual applications, the timing of the second-stage ADR2 can be programmed according to different application scenarios to better coordinate with the operating timing of the previous stage ADR and the next stage ADR to complete relay cooling, thereby achieving the goal of reducing the number of multi-temperature stage ADRs.

[0042] It can be understood that the above embodiment 1 of the application is only described as an example of a three-stage CADR structure, and other multi-constant-temperature-stage CADR (two-stage, four-stage, five-stage), multi-constant-temperature refrigeration temperature (60 mK, 400 mK, 2K, etc.), multi-constant-temperature heat sink temperature (2K, 6K) CADR are all applicable to the multi-constant-temperature-stage ADR structure and the operating strategy described in the patent.

[0043] The multi-constant-temperature-stage adiabatic demagnetization refrigerator provided by the application realizes the time sequence cooperation between the stages of the multi-stage series ADR by reasonably designing the thermal switch to connect the stages of the ADR and the heat load, and realizes the multi-constant-temperature continuous refrigeration for different heat loads by adjusting the operation time sequence between the stages of the ADR, and has a simple and compact structure.

[0044] It can be understood that the technical features of the above-described embodiments can be combined arbitrarily, and in order to make the description simple, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0045] The above is only a preferred embodiment of the application, and only the technical principle of the application is specifically described, and these descriptions are only for explaining the principle of the application, and cannot be explained as a limitation on the protection scope of the application in any way. Based on the explanation here, any modification, equivalent replacement and improvement made within the spirit and principle of the application, and other specific embodiments of the application that can be easily thought of by those skilled in the art without creative labor, should be included in the protection scope of the application.

Claims

1. A multi-thermostatic-stage adiabatic demagnetocaloric refrigerator, characterized by, The heat sink, the ADR body, the thermal switch and the thermal load, the ADR body comprising a first-stage ADR 1, a second-stage ADR 2 and a third-stage ADR 3, the thermal switch comprising a first thermal switch HS1, a second thermal switch HS2, a third thermal switch HS3 and a fourth thermal switch HS4, the thermal load comprising a first thermal load and a second thermal load, wherein: The two ends of the first thermal switch HS1 are connected with the heat sink and the first-stage ADR 1 respectively, the two ends of the second thermal switch HS2 are connected with the first-stage ADR 1 and the first thermal load respectively, the two ends of the third thermal switch HS3 are connected with the second-stage ADR 2 and the first thermal load respectively, the second thermal switch HS2 and the third thermal switch HS3 are connected between the first-stage ADR 1 and the second-stage ADR 2, the fourth thermal switch HS4 is connected between the second-stage ADR 2 and the third-stage ADR 3, and the other end of the fourth-stage ADR 4 is connected with the second thermal load.

2. The multi-thermally staged adiabatic demagnetisation refrigerator of claim 1, wherein, Each ADR body comprises paramagnetic salt pills (11) and superconducting magnets (12) surrounding the paramagnetic salt pills (11).

3. The multi-thermally-regulated adiabatic demagnetization refrigerator of claim 2, wherein, The paramagnetic salt pills are gadolinium gallium garnet or chrome potassium alum or gadolinium lithium fluoride or iron ammonium alum or ytterbium gallium garnet, and the superconducting magnets are niobium titanium or niobium tin.

4. The multi-thermally-regulated adiabatic demagnetization refrigerator of claim 1, wherein, The thermal switch comprises an air gap thermal switch or a superconducting thermal switch or a magnetoresistive thermal switch or a mechanical thermal switch.

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