A sample chamber for a liquid helium temperature scale platform

Abstract

The present invention relates to a sample chamber for a liquid helium temperature scale platform. Among them, the liquid helium temperature scale platform includes: the sample chamber, a cryogenic dewar, a cryogenic temperature control system, and a superconducting magnet system. The sample chamber is used to realize the replacement of samples without shutting down under a background magnetic field. The sample chamber includes a cavity and a sample rod. The cavity is installed at the center of the top cover and is connected to the cold shield through a heat sink thereon. The cavity extends downward to the heater. The sample rod is inserted into the sample chamber, and a sample holder is installed at the bottom. The superconducting magnet system is hoisted around the sample holder to generate a background magnetic field. Among them, the sample chamber is a closed cavity and isolates the vacuum environment of the superconducting magnet system, providing an independent vacuum space for the calibration of sensor samples, so that the replacement of samples does not affect the normal operation of the superconducting magnet system, and improves the efficiency of temperature sensor calibration.

Description

Technical Field

[0001] The present invention belongs to the fields of nuclear fusion technology and superconducting cryogenic technology, and particularly relates to a sample chamber for a liquid helium temperature scale platform, which can be used as a sample chamber that can be replaced without shutting down the machine for a liquid helium temperature scale platform under a magnetic field background. Background Art

[0002] In the field of metrology and measurement science, temperature measurement is a basic physical quantity. With the rapid development of many scientific and technological fields such as high-energy physics, superconducting technology, aerospace engineering, atomic energy science, and medicine, new requirements for temperature measurement at extremely low temperatures have been put forward, such as high accuracy, good reproducibility, easy use, low cost, and little influence by magnetic fields. Accurate temperature measurement and calibration in an ultra-low temperature magnetic field environment is an important issue, which directly affects the development of related research fields.

[0003] Large superconducting magnets in large scientific engineering projects such as domestic nuclear fusion devices, high-energy physics accelerator devices, and advanced light sources need to be equipped with large helium cryogenic systems for cooling. A large number of cryogenic temperature measurements are required for the entire device and its cryogenic system. At present, the price of the Cernox carbon resistance thermometer of the American LakeShore Company, which is the most used in the cryogenic field, after calibration is more than twice the price before calibration. Thermometers for cryogenic temperature measurement in a magnetic field environment also need to consider suitable alternative products. It is of great significance to carry out measurement tests on different types of cryogenic thermometers in the ultra-low temperature range under a magnetic field environment and develop theoretical research and engineering technology related to cryogenic measurement tests. Summary of the Invention

[0004] Aiming at the existing technical problems, the purpose of the present invention is to provide a sample chamber included in a liquid helium temperature scale platform, which can be used for sample replacement without shutting down the machine for a liquid helium temperature scale platform under a magnetic field background, saving the time of rewarming and cooling down again, and greatly improving the efficiency of temperature sensor calibration.

[0005] The technical solution of the present invention is as follows:

[0006] A sample chamber for a liquid helium temperature scale platform, wherein the liquid helium temperature scale platform includes: the sample chamber, a cryogenic dewar, a cryogenic constant temperature system, and a superconducting magnet system;

[0007] The cryogenic dewar consists of an outer vacuum chamber and a radiation protection cold shield located in the vacuum chamber. Among them, the vacuum chamber consists of a top cover, a cylinder body, and a vacuum unit that provides negative pressure, and the cold shield is hoisted in the cylinder body;

[0008] The sample chamber is used to replace samples without shutting down under the background magnetic field. The sample chamber includes a cavity and a sample rod. Among them, the cavity is installed at the center of the top cover and is connected to the cold shield through the heat sink thereon. The cavity extends downward to the heater. The sample rod is inserted into the sample chamber, and a sample holder is installed at the bottom.

[0009] The cryogenic constant temperature system consists of two GM refrigerators, which are respectively installed on both sides of the sample chamber, and the main body of the GM refrigerator extends into the vacuum chamber.

[0010] The superconducting magnet system is hoisted around the sample holder to generate a background magnetic field.

[0011] Among them, the sample chamber is a closed cavity, and isolates the vacuum environment of the superconducting magnet system, providing an independent vacuum space for the calibration of the sensor to be measured, so that the replacement of the sample does not affect the normal operation of the superconducting magnet system.

[0012] Among them, the cavity is mainly composed of a non-magnetic stainless steel tube, a mounting flange, a heat sink, a corrugated section, and a heat exchanger. The non-magnetic stainless steel tube is the main body of the cavity, and the mounting flange is welded to its top. The heat sink is welded at about 1 / 3 above the cavity. Two corrugated sections are arranged on the tube wall of the non-magnetic stainless steel tube, respectively above and below the heat sink. The heat exchanger is arranged below the non-magnetic stainless steel tube. The heat sink transfers the cold of the GM refrigerator to the cavity to reduce the heat leakage from the top cover to the sample test area.

[0013] Furthermore, the sample rod includes a top cover flange, a aviation plug, a pull rod, a radiation baffle, and a mounting plate. The bottom of the sample rod is threadedly connected to the sample holder through the mounting plate. The sample holder is provided with mounting holes for the temperature sensor to be measured, calibration sensor mounting holes, and a central gaussmeter probe mounting hole.

[0014] Furthermore, the liquid helium temperature scale platform also includes cryogenic temperature sensors. The cryogenic temperature sensors include the temperature sensor to be measured and the calibration temperature sensor, which are respectively installed in the holes for the temperature sensor to be measured and the calibration sensor. The cryogenic temperature sensors are led out by opening holes in the radiation baffle.

[0015] Furthermore, the cryogenic temperature sensors are fixed on copper seats, and a copper outer cylinder is used as a shielding cover to reduce the influence of the peripheral temperature zone on the cryogenic temperature sensors. At the same time, the disassembly is simple, which is convenient for the installation and replacement of samples. A copper wire mesh is added to the bottom of the copper seat, which can make the helium purge uniform, so as to obtain a uniform and stable temperature field.

[0016] Furthermore, the cavity includes two corrugated sections, which can extend the cavity stroke, greatly reduce the heat leakage of the system. At the same time, the wall thickness of the outer tube of the cavity is reduced, the cross-sectional area is reduced, and the heat leakage is reduced.

[0017] Furthermore, the holes for the temperature sensors to be measured are equally spaced between each circle from the inside to the outside, and are arranged at equal angles within each circle. The holes for the calibration sensors are arranged at equal radial distances.

[0018] Furthermore, the pull rod is threadedly connected to the radiation baffle, which is convenient for installation and disassembly. The radiation baffle has misaligned openings for easy wiring.

[0019] As can be seen from the technical solution provided by the present invention above, the beneficial effects of the present invention are as follows:

[0020] The sample chamber of the present invention can adopt a multi-section structure, which connects two welded corrugated sections, increases the solid travel of the sample chamber, reduces the solid heat leakage, welds a copper heat sink seat on the outer surface of the middle of the sample chamber, uses copper braiding to connect the cold shield top cover for heat insulation design, and reduces the heat leakage of the sample chamber. The pumping return gas pipeline also adopts welded corrugated sections and heat insulation to reduce the heat leakage of the system to the sample chamber.

[0021] The sample chamber of the present invention is a closed chamber, which isolates the vacuum environment of the background field superconducting magnet system, provides an independent vacuum space for the calibration of sensor samples, and enables the replacement of samples without affecting the normal operation of the background field superconducting magnet system; the sample chamber is a closed and independent environment, and can realize sample replacement without stopping the machine, saving the time cost of temperature calibration.

[0022] The helium temperature scale platform of the present invention is provided with a rewarming heater, which is installed at the outlet of the vacuum chamber, can reduce the temperature difference and prevent the generation of steam condensate; the rewarming heater is installed in front of the dry pump, which is beneficial to extend the service life; a nitrogen gas cylinder can be conveniently installed to further accelerate the rewarming speed above 80K.

[0023] A metal mesh is added to the bottom of the seat of the sample rod of the present invention to make the helium purge uniform, so as to obtain a uniform and stable temperature field. In addition, the pull rod of the sample rod is threadedly connected to the radiation baffle, which is convenient for installation and disassembly, and the radiation baffle has misaligned openings for easy wiring. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 It is a schematic structural diagram of a cryogenic temperature calibration system in the superfluid helium temperature region under a magnetic field environment provided by an embodiment of the present invention;

[0026] Figure 2 It is a schematic diagram of the sample chamber;

[0027] Figure 3 It is a schematic diagram of the sample rack.

[0028] 1—1# GM refrigerator, 2—pre-cooling pipeline, 3—sample rod, 4—2# GM refrigerator, 5—vacuum chamber, 6—cold screen, 7—superconducting magnet, 8—sample rack, 9—heater, 10—condenser, 11—regenerator, 12—circulation pipeline, 13—1# manual ball valve, 14—2# manual ball valve, 15—3# manual needle valve, 16—4# manual ball valve, 17—5# manual ball valve, 18—molecular pump, 19—circulation pump, 20—helium gas cylinder, 21—6# manual ball valve, 22—buffer tank, 23—flowmeter, 24—7# manual ball valve, 25—8# manual ball valve, 26—top cover, 27—warming heater, 28—molecular pump of vacuum chamber, 29—gate valve, 30—lifting ring, 31—connector, 32—top cover flange, 33—mounting flange, 34—corrugated section 1, 35—heat sink, 36—corrugated section 2, 37—non-magnetic stainless steel pipe, 38—radiation baffle, 39—pull rod, 40—mounting plate, 42—calibration sensor mounting hole, 43—temperature sensor mounting hole to be measured, 44—central gaussmeter probe mounting hole. Detailed implementation manners

[0029] Next, in combination with the drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] Next, the sample chamber that can replace the sample chamber without stopping the machine for the liquid helium temperature scale platform under the magnetic field background provided by the present invention will be described in detail.

[0031] As Figure 1 shown, a sample chamber for a liquid helium temperature scale platform, the sample chamber is used to realize non-stop sample replacement of the liquid helium temperature scale platform under the magnetic field background, including a cavity body and a sample rod 3, for the liquid helium temperature scale platform under the magnetic field background.

[0032] The liquid helium temperature scale platform includes: a cryogenic dewar, a sample chamber, a cryogenic constant temperature system, and a superconducting magnet system. Among them, the cryogenic dewar is composed of an outer vacuum chamber 5 and a radiation-proof cold screen located in the vacuum chamber. Among them, the vacuum chamber 5 is composed of a top cover 26 and a cylinder body, and a vacuum unit that provides negative pressure, and the cold screen 6 is hoisted in the cylinder body;

[0033] The sample chamber is used to replace samples without stopping under a background magnetic field. The sample chamber includes a cavity and a sample rod 3. The cavity is installed at the center of the top cover and is connected to the cold shield through a heat sink thereon. The cavity extends downward to a heater 9. The sample rod 3 is inserted into the sample chamber, and a sample holder 8 is provided at the bottom.

[0034] The cryogenic constant temperature system consists of two GM cryocoolers, which are respectively installed on both sides of the sample chamber, and the main part of the GM cryocooler extends into the vacuum chamber.

[0035] The superconducting magnet system is hoisted around the sample holder to generate a background magnetic field.

[0036] Among them, the sample chamber is a closed cavity, isolating the vacuum environment of the superconducting magnet system, providing an independent vacuum space for the calibration of sensor samples, so that the replacement of samples does not affect the normal operation of the superconducting magnet system.

[0037] The cryogenic measurement and control device is configured with measurement instruments such as cryogenic temperature sensors and pressure transmitters, as well as temperature controllers and acquisition and control devices.

[0038] Among them, the vacuum unit includes 1 vacuum loop and 2 sets of vacuum pump groups: one set of circulation pump is used for helium circulation and decompression to obtain a superfluid helium temperature range of 1.8K, and one set of molecular pump 18 is used for pumping and maintaining the vacuum degree of the cryogenic constant temperature system and the sample chamber.

[0039] Among them, the cavity is mainly composed of a non-magnetic stainless steel tube, a mounting flange, a heat sink, corrugated sections, and a heat exchanger. The non-magnetic stainless steel tube is the main body of the cavity, and its top is welded with a mounting flange. The heat sink is welded at about 1 / 3 above the cavity. Two corrugated sections are provided on the tube wall of the non-magnetic stainless steel tube, respectively above and below the heat sink. The heat exchanger is arranged below the non-magnetic stainless steel tube. The heat sink transfers the cold of the GM cryocooler to the cavity to reduce the heat leakage influence of the top cover on the sample test area.

[0040] As shown in the Figure 2 attachment, the sample rod includes a top cover flange 32, a aviation plug 31, a pull rod 39, a radiation baffle 38, and a mounting plate 40. The bottom of the sample rod is threadedly connected to the sample holder 8 through the mounting plate 40. The sample holder 8 is provided with a measured temperature sensor mounting hole 43, a calibration sensor mounting hole 42, and a central gaussmeter probe mounting hole 44.

[0041] The liquid helium temperature scale platform also includes a cryogenic temperature sensor. The cryogenic temperature sensor includes a measured temperature sensor and a calibration temperature sensor, which are respectively installed in the measured temperature sensor mounting hole 43 and the calibration sensor mounting hole 42, as Figure 3As shown. The low-temperature temperature sensor is led out by opening a hole in the radiation baffle 38.

[0042] Among them, the low-temperature temperature sensor is fixed on a copper seat, and a copper outer cylinder is used as a shielding cover to reduce the influence of the peripheral temperature zone on the low-temperature temperature sensor. A copper wire mesh is installed at the bottom of the copper seat, which can make the helium purge uniform, so as to obtain a uniform and stable temperature field.

[0043] Furthermore, the sample chamber of the embodiment of the present invention adopts a multi-section structure, connecting two welded corrugated sections, increasing the solid travel of the sample chamber, reducing the solid heat leakage. A copper heat sink seat is welded on the outer surface of the middle of the sample chamber, and the cold shield top cover is connected by copper braiding for heat insulation design to reduce the heat leakage of the sample chamber. The pumping return gas pipeline also adopts welded corrugated sections and heat insulation to reduce the heat leakage of the system to the sample chamber.

[0044] The sample chamber of the embodiment of the present invention is a closed chamber, isolating the vacuum environment of the background field superconducting magnet system, providing an independent vacuum space for the calibration of sensor samples, and enabling the replacement of samples without affecting the normal operation of the background field superconducting magnet system. Since the sample chamber of the embodiment of the present invention is a closed and independent environment, it is possible to replace samples without shutting down, saving the time cost of temperature sensor calibration.

[0045] In addition, a warm-up heater 27 is also provided on the liquid helium temperature scale platform of the embodiment of the present invention. The warm-up heater 27 is installed at the gas outlet, which can reduce the temperature difference and prevent the generation of steam condensate. The warm-up heater is installed in front of the circulation pump 19, which is beneficial to extending the service life; preferably, a nitrogen cylinder can be additionally installed outside the buffer tank 22 to further accelerate the warm-up speed above 80K.

[0046] A metal mesh is installed at the bottom of the seat of the sample rod 3 of the embodiment of the present invention to make the helium purge uniform, so as to obtain a uniform and stable temperature field. The pull rod of the sample rod 3 is threadedly connected to the radiation baffle, which is convenient for installation and disassembly. The radiation baffle is misaligned with holes for easy wiring.

[0047] Specifically, the working process of the replaceable sample chamber without shutting down for the liquid helium temperature scale platform under magnetic field background of the present invention may include the following steps:

[0048] 1. Evacuate the vacuum chamber and the sample chamber

[0049] Open the molecular pump 28 and gate valve 29 of the vacuum chamber, and first evacuate the vacuum chamber 5. When the vacuum degree of the vacuum chamber 5 reaches 0.5 (at room temperature), close the gate valve 29 to maintain the vacuum degree of the vacuum chamber 5. Open the molecular pump 18, open the 8# manual ball valve 25, 7# manual ball valve 24, 2# manual ball valve 14, 1# manual ball valve 13, 3# manual needle valve 15, 5# manual ball valve 17, and then evacuate the sample chamber, external pipeline, and buffer tank 22 of the internal pipeline. When the vacuum degree of the sample chamber reaches 0.1 Pa (at room temperature), close the valves of the 7# manual ball valve 24, 1# manual ball valve 13, 3# manual needle valve 15, 4# manual ball valve 16, and 5# manual ball valve 17. Fill helium into the buffer tank 22 through the high-pressure helium gas cylinder, and then close the 6# manual ball valve 21. Open the molecular pump 18 for the second time, open the 8# manual ball valve 25, 7# manual ball valve 24, 2# manual ball valve 14, 1# manual ball valve 13, 3# manual needle valve 15, 5# manual ball valve 17, and then evacuate the sample chamber, external pipeline, and buffer tank 22 of the internal pipeline. When the vacuum degree of the sample chamber reaches 0.1 Pa (at room temperature), close the valves of the 7# manual ball valve 24, 1# manual ball valve 13, 3# manual needle valve 15, 4# manual ball valve 16, and 5# manual ball valve 17.

[0050] 2. Helium filling and circulation

[0051] Fill slightly positive pressure helium (1.1 bara) into the buffer tank 22 through the high-pressure helium gas cylinder, and then close the 6# manual ball valve 21. Open the circulation pump 19, and the helium circulates through the 8# manual ball valve 25 in the high-temperature loop. When the temperature of the sample chamber is 4.2 K, close the 8# manual ball valve 25 and open the 7# manual ball valve 24 for low-temperature loop circulation.

[0052] 3. Refrigerator cooling cycle pre-cooling

[0053] Start the two refrigerators, the 2# GM refrigerator 4 and the 1# GM refrigerator 1, simultaneously for cooling, and keep the circulation pump 19 circulating. Finally, the magnet temperature drops to about 4 K; the temperature of the sample chamber is 1.8 K, and the readings of the low-temperature temperature sensors arranged on the sample rack are all 1.8 K.

[0054] 4. Heating and temperature control 1 (1.8 K - 4.2 K)

[0055] After the temperature drops to the lowest, the temperature of the sample chamber is 1.8 K. After the temperature stabilizes, calibrate the sensor to be calibrated. Then, heat the outlet helium through the heater 9 to calibrate the sensor to be calibrated in the temperature range of 1.8 K - 4.2 K.

[0056] 5. Sample chamber rewarming and repressurization

[0057] Turn off GM refrigerator 1, cut off the power supply of the magnet, open manual ball valve 14 of No. 2 and manual ball valve 25 of No. 8, turn on heater 9 and rewarming heater 27, heat the helium gas in the pipeline to rewarm the cavity to 300K, open manual ball valve 16 of No. 4, turn on the molecular pump 18, control the pressure in the sample chamber to return to atmospheric pressure, and then stop the gas circuit;

[0058] 6. Replace the sample chamber

[0059] After the calibration of the bottom sensor of the sample holder is completed, take out the sample rod 3 in the cavity, quickly insert another set of sample rods with sensors, and after installation, repeat the above steps to calibrate it.

[0060] As described above, it is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A sample chamber for a liquid helium temperature scale platform, the liquid helium temperature scale platform comprises: the sample chamber, a cryogenic dewar, a cryogenic temperature control system and a superconducting magnet system, characterized in that: the cryogenic dewar consists of an outer vacuum chamber and a radiation shield located in the vacuum chamber. Among them, the vacuum chamber consists of a top cover, a cylinder body and a vacuum unit providing negative pressure, and the cold screen is hoisted in the cylinder body; the sample chamber is used to realize the replacement of samples without shutting down under the background magnetic field. The sample chamber includes a cavity body and a sample rod; wherein the cavity body is installed at the center of the top cover and is connected to the cold screen through the heat sink thereon. The cavity body extends downward to a heater, and the sample rod is inserted into the sample chamber, and a sample rack is installed at the bottom; the cryogenic temperature control system consists of two GM cryocoolers, which are respectively installed on both sides of the sample chamber, and the main body parts of the GM cryocoolers extend into the vacuum chamber; the superconducting magnet system is hoisted around the sample rack and is used to generate a background magnetic field; wherein, the sample chamber is a closed cavity and isolates the vacuum environment of the superconducting magnet system, providing an independent vacuum space for the calibration of the sensor to be measured, so that the replacement of the sample does not affect the normal operation of the superconducting magnet system; wherein, the cavity body is composed of a non-magnetic stainless steel tube, a mounting flange, a heat sink, a corrugated section and a heat exchanger. The non-magnetic stainless steel tube is the main body of the cavity body, and its top is welded with a mounting flange. The heat sink is welded at the upper 1 / 3 of the cavity body. Two corrugated sections are arranged on the tube wall of the non-magnetic stainless steel tube, respectively above and below the heat sink. The heat exchanger is arranged below the non-magnetic stainless steel tube. The heat sink transfers the cold of the GM cryocooler to the cavity body to reduce the heat leakage influence of the top cover on the sample test area.

2. A sample chamber for a liquid helium temperature scale platform according to claim 1, characterized in that: the sample rod includes a top cover flange, a aviation plug, a pull rod, a radiation baffle and a mounting plate; the bottom of the sample rod is threadedly connected to the sample rack through the mounting plate; the sample rack is provided with a mounting hole for a temperature sensor to be measured, a calibration sensor mounting hole and a central gaussmeter probe mounting hole.

3. A sample chamber for a liquid helium temperature scale platform according to claim 2, characterized in that: the liquid helium temperature scale platform further includes a cryogenic temperature sensor, and the cryogenic temperature sensor includes a temperature sensor to be measured and a calibration temperature sensor, which are respectively installed in the mounting holes for the temperature sensor to be measured and the calibration sensor. The cryogenic temperature sensor leads wires by opening holes on the radiation baffle.

4. A sample chamber for a liquid helium temperature scale platform according to claim 3, characterized in that: the cryogenic temperature sensor is fixed on a copper seat and uses a copper outer cylinder as a shielding cover to reduce the influence of the peripheral temperature zone on the cryogenic temperature sensor. A copper wire mesh is installed at the bottom of the copper seat, which can make the helium gas purge evenly, so as to obtain a uniform and stable temperature field.

5. A sample chamber for a liquid helium temperature scale platform according to claim 1, characterized in that: the cavity body includes two corrugated sections.

6. A sample chamber for a liquid helium temperature scale platform according to claim 3, characterized in that: The holes of the temperature sensor to be measured are equidistantly distributed between each circle from the inside to the outside, and are arranged at equal angles within each circle. The calibration sensor holes are arranged at equal radial distances.

7. A sample chamber for a liquid helium temperature scale platform according to claim 3, characterized in that: The pull rod is threadedly connected to the radiation baffle, and the radiation baffle has offset holes.

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