Cold head container for liquid-helium-free superconducting magnet and use method of cold head container

Abstract

The invention discloses a cold head container for a liquid-helium-free superconducting magnet and a using method of the cold head container, and belongs to the technical field of superconducting magnetic resonance equipment.The cold head container comprises a first-level container heat transfer block and a second-level container heat transfer block, a sleeve is arranged above the first-level container heat transfer block, and the bottom end of the sleeve is fixedly communicated with a through hole of the first-level container heat transfer block; an upper flange is fixedly installed at the top end of the sleeve, a connecting flange is fixedly installed above the upper flange, a plurality of evacuation sealing valves are arranged on the peripheral side of the connecting flange and communicate with the interior of the sleeve, and a plurality of evenly-distributed flexible cold guide plates are fixedly connected to the peripheral side of the container primary heat transfer block. A connecting pipe and a corrugated pipe are arranged between the container primary heat transfer block and the container secondary heat transfer block; the using method of the cold head container comprises the steps that S1, the magnet is pre-cooled; s2, dismounting the pre-cooling assembly; s3, mounting the refrigeration component; according to the cold head container, the pre-cooling time of the magnet can be remarkably shortened, and meanwhile, the refrigeration part is more convenient to replace.

Description

Technical Field

[0001] The invention belongs to the technical field of superconducting magnetic resonance equipment, and in particular relates to a cold head container for a liquid helium-free superconducting magnet and a use method thereof. Background Art

[0002] In the existing liquid helium-free superconducting magnets, the magnets are generally cooled by GM refrigerators. GM refrigerators are generally divided into two stages. The first stage provides a cooling capacity of tens of watts in the temperature range of 30-80K, and the second stage provides a cooling capacity of 1-2W at about 4.2K. The 4K magnet coil is connected to the second stage of the refrigerator, and the first stage of the refrigerator is connected to the cold shield of the magnet. The cooling speed of the magnet in the early stage is mainly determined by the cooling speed of the 4K magnet with a larger cold mass. Therefore, if the temperature of the 4K magnet part can be quickly reduced to about the liquid nitrogen temperature, the cooling time of the liquid helium-free magnet will be greatly shortened. The traditional magnet liquid nitrogen pre-cooling is to arrange pipelines inside the vacuum cavity of the magnet outer cylinder, and the pipeline inlet and outlet are outside the magnet outer cylinder. Due to the sealing problem, when liquid nitrogen is input into the pipeline, the vacuum degree in the magnet outer cylinder will deteriorate. As the vacuum degree deteriorates, the pre-cooling effect of liquid nitrogen in the pipeline becomes worse and worse, resulting in the pre-cooling failing to achieve the expected effect; there are also patents in the prior art for introducing the first-stage cooling capacity into the coil, but the structure is complex and the effect is limited. In addition, the secondary cold head of the traditional refrigerator is in direct contact with the 4K magnet. Once the refrigerator fails and needs to be replaced, the magnet must be removed first, then the vacuum is destroyed, and then the refrigerator can be replaced. The replacement process is cumbersome and will prolong the subsequent cooling time.

[0003] In summary, the common problems in the use of liquid helium-free magnets are: 1. The cooling time of the magnet is longer than that of the magnet with liquid helium; 2. When the cold head of the liquid helium-free magnet is replaced, the vacuum of the magnet will be destroyed, causing the temperature of the magnet to rise rapidly. After the cold head is replaced, it is necessary to re-evacuate the vacuum, and the cooling time is slow. In addition, when replacing the cold head, the magnet must be de-fielded, and the replacement process is cumbersome. Summary of the invention

[0004] In order to solve the problems raised in the background technology, the purpose of the present invention is to provide a cold head container for a liquid helium-free superconducting magnet and a method of using the same, aiming to shorten the pre-cooling time and reduce the pre-cooling cost. At the same time, the refrigerator and other accessories in the refrigeration component can be quickly replaced without destroying the vacuum degree of the outer cylinder of the magnet and maintaining the magnetic field.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A cold head container for a liquid helium-free superconducting magnet comprises a first-stage heat transfer block with a through hole in the center and a second-stage heat transfer block of a cylindrical container, a sleeve is arranged above the first-stage heat transfer block, the bottom end of the sleeve is fixedly connected with the through hole of the first-stage heat transfer block, an upper flange is fixedly mounted on the top end of the sleeve, a connecting flange is fixedly mounted above the upper flange, a plurality of evacuation sealing valves are arranged on the outer peripheral side of the connecting flange, the evacuation sealing valves are connected with the inside of the sleeve, a plurality of uniformly distributed flexible cold conduction plates are fixedly connected to the peripheral side of the first-stage heat transfer block, and a connecting pipe and a bellows are arranged between the first-stage heat transfer block and the second-stage heat transfer block.

[0007] Furthermore, the shape of the primary heat transfer block of the container can be square or circular, and the diameter of the through hole is smaller than the diameter of the sleeve.

[0008] Furthermore, a first sealing ring is embedded and installed on the top surface of the connecting flange, and the first sealing ring can seal the installation position of the cover plate or the refrigerator and the connecting flange.

[0009] Furthermore, a second sealing ring is embedded and installed between the connecting flange and the upper flange, and the second sealing ring is used to seal between the upper flange and the connecting flange.

[0010] Furthermore, the bottom end of the first heat transfer block of the container is fixedly connected to the top end of the connecting pipe, the bottom end of the connecting pipe is fixedly connected to the top end of the bellows, and the bottom end of the bellows is fixedly connected to the top end of the second heat transfer block of the container; the arrangement of the bellows can prevent the refrigerator from transmitting vibration to the second heat transfer block of the container when working.

[0011] Furthermore, the connections between the upper flange and the sleeve, between the sleeve and the first-level heat transfer block of the container, between the first-level heat transfer block of the container and the connecting pipe, between the connecting pipe and the bellows, and between the bellows and the second-level heat transfer block of the container are all sealed connections.

[0012] Furthermore, the container primary heat transfer block, the container secondary heat transfer block and the flexible cold conduction plate are all made of solid heat conductive material, and the solid heat conductive material may be oxygen-free copper.

[0013] A method for using a cold head container for a liquid helium-free superconducting magnet comprises the following steps:

[0014] S1. Magnet precooling:

[0015] Install the cold head container in the superconducting magnetic resonance equipment and evacuate the interior of the magnet outer cylinder to 10 -4Pa, then the cover plate of the precooling assembly is fixedly sealed with the connecting flange, and then the interior of the cold head container is evacuated through the evacuation sealing valve. After evacuation, liquid nitrogen is introduced into the cold head container through the inlet ball valve, and the outlet ball valve is kept open. The gasified nitrogen is discharged from the outlet ball valve until liquid begins to accumulate inside the cold head container, and the precooling is completed; through this precooling, the magnet cold shield inside the magnet and the cooling path of the magnet coil skeleton are used to cool the magnet, eliminating the trouble of installing a precooling pipeline inside the magnet, and the structure is simple and the effect is good;

[0016] S2. Removal of precooling components:

[0017] Fill the cold head container with nitrogen through the inlet ball valve, discharge the liquid nitrogen and purge the cold head container with nitrogen, close the inlet ball valve and the outlet ball valve in turn, then quickly remove the cover plate and move the pre-cooling assembly out;

[0018] S3. Installation of refrigeration components:

[0019] Quickly insert the output end of the refrigerator into the cold head container. After the refrigerator body and the connecting flange are fixedly installed, purge helium into the cold head container through the vacuum sealing valve. After the purge is completed, evacuate the cold head container through the vacuum sealing valve. After evacuation, start the refrigerator for cooling. The refrigerator further cools the container's first-level heat transfer block and the container's second-level heat transfer block through the first-level cold head and the second-level cold head, and finally cools the magnet to the working temperature. The cooling time of the entire magnet will be greatly shortened. In addition, if the cold head of the refrigerator fails later, the cold head of the refrigerator can be directly pulled out of the cold head container without destroying the vacuum inside the magnet, and then a new refrigerator or cold head can be replaced, which greatly facilitates the subsequent maintenance of the cold head of the refrigerator.

[0020] Furthermore, the cold head container is installed in a superconducting magnetic resonance device, including fixing and sealing the upper flange to the outer cylinder of the magnet, fixing the end of the flexible cold plate to the magnet cold shield, and fixing the bottom end of the container's secondary heat transfer block to the magnet coil frame.

[0021] Furthermore, the vacuum degree of the cold head container is less than 5Pa.

[0022] Beneficial effects of the present invention:

[0023] The present invention provides a cold head container for a liquid helium-free superconducting magnet. The cold head container is an independent vacuum container. On the one hand, when the magnet is pre-cooled, it can be used as a liquid nitrogen storage tank. Through continuous liquid nitrogen circulation, the first-level heat transfer block and the second-level heat transfer block of the cold head container are gradually cooled to the liquid nitrogen temperature. Then, as a cold source, the magnet cold shield and the magnet coil skeleton are cooled to the liquid nitrogen temperature through solid heat conductive materials. There is no pipeline leakage and external pipeline heat leakage problem. The structure is simple, the operation is convenient, and the efficiency is remarkable. On the other hand, under normal working conditions, As the support of the refrigerator, the first-level cold head and the second-level cold head are in close contact with the first-level heat transfer block and the second-level heat transfer block of the container respectively. When the refrigerator is started, the first-level heat transfer block and the second-level heat transfer block of the container can be quickly cooled from the liquid nitrogen temperature to about 4.2K, which greatly shortens the overall cooling time of the magnet. When replacing the cold head, it is only necessary to take the cold head out of the cold head container without destroying the vacuum inside the magnet. In this way, the temperature rise inside the magnet is relatively small. After the cold head is reopened, the cooling time is short, which provides great convenience for subsequent cold head maintenance.

[0024] The present invention arranges a cold head container so that the secondary cold head does not directly contact the inside of the magnet. When the refrigerator fails to be repaired or the refrigeration components need to be replaced, the vacuum inside the magnet will not be destroyed and the magnet does not need to be lowered. This solves the problem of complicated procedures for refrigerator maintenance or cold head replacement in the prior art, shortens the time for later refrigerator or cold head replacement, and improves work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below in conjunction with the accompanying drawings.

[0026] Figure 1 is a three-dimensional diagram of a cold head container of the present invention;

[0027] Figure 2 is a cross-sectional view of a cold head container of the present invention;

[0028] Figure 3 yes Figure 2 A partial enlarged view of the middle A;

[0029] Figure 4 It is a structural schematic diagram of the refrigeration component of the present invention;

[0030] Figure 5 It is a schematic diagram of the structure of the refrigeration component of the present invention when it is assembled and used with the cold head container;

[0031] Figure 6 It is a schematic diagram of the structure of the precooling assembly of the present invention;

[0032] Figure 7 It is a structural schematic diagram of the precooling component and the cold head container of the present invention when they are assembled and used.

[0033] In the figure: 101, sleeve; 1011, upper flange; 102, container secondary heat transfer block; 103, connecting flange; 1031, first sealing ring; 1032, evacuation sealing valve; 1033, second sealing ring; 104, container primary heat transfer block; 105, flexible cold conduction plate; 106, connecting pipe; 107, bellows; 2, refrigeration component; 201, refrigerator; 202, primary cold head; 203, secondary cold head; 3, magnet outer cylinder; 4, magnet cold screen; 5, magnet coil skeleton; 6, pre-cooling assembly; 601, cover plate; 602, inlet ball valve; 603, infusion tube; 604, outlet ball valve; 605, one-way pressure valve. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] See also Figure 1-Figure 3 As shown, this embodiment provides a cold head container for a liquid helium-free superconducting magnet, comprising a first-level heat transfer block 104 with a through hole in the center and a second-level heat transfer block 102 of a cylindrical shape. A sleeve 101 is provided above the first-level heat transfer block 104. The bottom end of the sleeve 101 is fixedly connected to the center of the first-level heat transfer block 104. An upper flange 1011 is fixedly mounted on the top of the sleeve 101. A connecting flange 103 is fixedly mounted above the upper flange 1011. A first sealing ring 1031 is embeddedly mounted on the top surface of the connecting flange 103. A second sealing ring 1031 is embeddedly mounted between the connecting flange 103 and the upper flange 1011. 033. A plurality of evacuation sealing valves 1032 are arranged on the outer peripheral side of the connecting flange 103. The evacuation sealing valves 1032 are communicated with the interior of the sleeve 101. A plurality of uniformly distributed flexible cold conduction plates 105 are fixedly connected to the peripheral side of the first-level heat transfer block 104 of the container. A connecting pipe 106 and a bellows 107 are arranged between the first-level heat transfer block 104 of the container and the second-level heat transfer block 102 of the container. The bottom end of the first-level heat transfer block 104 of the container is fixedly connected to the top end of the connecting pipe 106. The bottom end of the connecting pipe 106 is fixedly connected to the top end of the bellows 107. The bottom end of the bellows 107 is fixedly connected to the top end of the second-level heat transfer block 102 of the container.

[0037] When the cold head container of the present invention is installed in a superconducting magnetic resonance device, it is fixedly and sealedly connected to the magnet outer cylinder 3 through the upper flange 1011, the end of the flexible cold conduction plate 105 is fixedly connected to the magnet cold shield 4, and the bottom end of the container secondary heat transfer block 102 is fixedly connected to the magnet coil skeleton 5.

[0038] Example 2

[0039] See also Figure 4-Figure 5 As shown, the refrigeration component 2 includes a refrigerator 201, and a primary cold head 202 and a secondary cold head 203 are fixedly installed at the output end of the refrigerator 201;

[0040] Under normal working conditions, the output end of the refrigerator 201 is located inside the cold head container, the refrigerator 201 body is fixedly connected to the connecting flange 103, the peripheral side of the first-level cold head 202 abuts against the first-level heat transfer block 104 of the container, and the peripheral side of the second-level cold head 203 abuts against the second-level heat transfer block 102 of the container.

[0041] Example 3

[0042] See also Figure 6-Figure 7 As shown, the precooling assembly 6 includes a circular cover plate 601, and an inlet ball valve 602, an outlet ball valve 604 and a one-way pressure valve 605 are arranged at the center of the cover plate 601. The inlet ball valve 602, the outlet ball valve 604 and the one-way pressure valve 605 are all sealed and connected to the other side of the cover plate 601, and the bottom end of the inlet ball valve 602 is fixedly connected to the infusion tube 603; the one-way pressure valve 605 serves as a safety valve to prevent the pressure in the cold head container from being too high and causing dangerous accidents;

[0043] In the pre-cooling state, the liquid infusion tube 603 extends into the secondary heat transfer block 102 of the container, and the cover plate 601 is fixedly and hermetically connected to the connecting flange 103 .

[0044] Example 4

[0045] This embodiment provides a method for using a cold head container for a liquid helium-free superconducting magnet, comprising the following steps:

[0046] S1. Magnet precooling:

[0047] Install the cold head container in the superconducting magnetic resonance device and evacuate the interior of the magnet outer cylinder 3 to 10 -4Pa, then the cover plate 601 of the precooling assembly 6 is fixedly and sealedly connected to the connecting flange 103, and then the interior of the cold head container is evacuated to less than 5Pa through the evacuation sealing valve 1032, and the liquid nitrogen dewar is connected to the inlet ball valve 602, and the inlet ball valve 602 is opened, and the liquid nitrogen enters the cold head container through the liquid infusion tube 603, and then the outlet ball valve 604 is kept open, and the gasified nitrogen is discharged from the outlet ball valve 604. Through continuous liquid nitrogen circulation, the temperature in the cold head container gradually decreases, and liquid begins to accumulate in the cold head container (which can be judged from the nitrogen pressure discharged from the outlet ball valve 604), indicating that the temperatures of the first-level heat transfer block 104 and the second-level heat transfer block 102 of the container have both dropped to about 77K, the temperature of liquid nitrogen. At this time, the two poles of the cold head container are equivalent to a cold source with liquid nitrogen temperature, and the magnet cold shield 4 and the magnet coil skeleton 5 are also reduced to about 77K, the temperature of liquid nitrogen through heat conduction. After standing for a period of time until the temperature is basically stable, the precooling is completed;

[0048] S2. Dismantling of precooling assembly 6:

[0049] After closing the inlet ball valve 602, remove the liquid nitrogen dewar, then connect the outlet of the nitrogen bottle to the inlet ball valve 602, open the inlet ball valve 602, fill the cold head container with nitrogen, discharge the liquid nitrogen and purge the cold head container with nitrogen, close the inlet ball valve 602 and the outlet ball valve 604 in turn, remove the nitrogen bottle, and then quickly remove the cover plate 601 to move the precooling assembly 6 out;

[0050] S3. Installation of refrigeration component 2:

[0051] The output end of the refrigerator 201 is quickly inserted into the cold head container. After the main body of the refrigerator 201 is fixedly installed with the connecting flange 103, the helium input pipeline is connected to the vacuum sealing valve 1032, and the vacuum sealing valve 1032 is opened to purge the cold head container with helium. After the purge is completed, the vacuum sealing valve 1032 is closed and the helium input pipeline is removed. The vacuum end of the vacuum pump is connected to the vacuum sealing valve 1032, and the vacuum sealing valve 1032 is opened to evacuate the cold head container. When the vacuum degree is less than 5Pa, the refrigerator 201 is started for cooling. The refrigerator 201 further cools the container's primary heat transfer block 104 and the container's secondary heat transfer block 102 through the primary cold head 202 and the secondary cold head 203, and finally cools the magnet from about 77K to the operating temperature of about 4.2K.

[0052] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0053] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A cold head container for a liquid helium-free superconducting magnet, characterized in that: The invention comprises a primary heat transfer block (104) of a container with a through hole in the center and a secondary heat transfer block (102) of a cylindrical container. A sleeve (101) is arranged above the primary heat transfer block (104). The bottom end of the sleeve (101) is fixedly connected to the through hole of the primary heat transfer block (104). An upper flange (1011) is fixedly installed on the top of the sleeve (101). A connecting flange (103) is fixedly installed above the upper flange (1011). A plurality of evacuation sealing valves (1032) are arranged on the outer peripheral side of the connecting flange (103). The evacuation sealing valves (1032) are connected to the inside of the sleeve (101). A plurality of uniformly distributed flexible cold conduction plates (105) are fixedly connected to the peripheral side of the primary heat transfer block (104). A connecting pipe (106) and a bellows (107) are arranged between the primary heat transfer block (104) and the secondary heat transfer block (102).

2. A cold head container for a liquid helium-free superconducting magnet according to claim 1, characterized in that: The diameter of the through hole is smaller than the diameter of the sleeve (101).

3. The cold head container for a liquid helium-free superconducting magnet according to claim 1, characterized in that: A first sealing ring (1031) is embedded and installed on the top surface of the connecting flange (103).

4. The cold head container for a liquid helium-free superconducting magnet according to claim 1, characterized in that: A second sealing ring (1033) is embedded and installed between the connecting flange (103) and the upper flange (1011).

5. The cold head container for a liquid helium-free superconducting magnet according to claim 1, characterized in that: The bottom end of the primary heat transfer block (104) of the container is fixedly connected to the top end of the connecting pipe (106), the bottom end of the connecting pipe (106) is fixedly connected to the top end of the bellows (107), and the bottom end of the bellows (107) is fixedly connected to the top end of the secondary heat transfer block (102) of the container.

6. The cold head container for a liquid helium-free superconducting magnet according to claim 1, characterized in that: The connections between the upper flange (1011) and the sleeve (101), between the sleeve (101) and the primary heat transfer block (104) of the container, between the primary heat transfer block (104) of the container and the connecting pipe (106), between the connecting pipe (106) and the bellows (107), and between the bellows (107) and the secondary heat transfer block (102) of the container are all sealed connections.

7. The cold head container for a liquid helium-free superconducting magnet according to claim 1, characterized in that: The container primary heat transfer block (104), the container secondary heat transfer block (102) and the flexible cold conduction plate (105) are all made of solid heat conducting material.

8. The method for using the cold head container according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Install the cold head container in the superconducting magnetic resonance device and evacuate the interior of the magnet outer cylinder (3) to 10 -4 Pa, then the precooling assembly (6) is installed and connected to the cold head container, and the interior of the cold head container is evacuated through the evacuation sealing valve (1032). After evacuation, liquid nitrogen is introduced into the cold head container through the inlet ball valve (602), and the outlet ball valve (604) is kept open until liquid begins to accumulate inside the cold head container, and the precooling is completed; S2, filling nitrogen into the cold head container through the inlet ball valve (602), discharging liquid nitrogen and purging the cold head container with nitrogen, closing the inlet ball valve (602) and the outlet ball valve (604) in turn, then removing the cover plate (601) and moving the precooling assembly (6) out; S3, the refrigeration component (2) is installed and connected with the cold head container, and helium is purged into the cold head container through the evacuation sealing valve (1032). After the purging is completed, the cold head container is evacuated through the evacuation sealing valve (1032). After the evacuation, the refrigerator (201) is started for cooling. The refrigerator (201) further cools the container's primary heat transfer block (104) and the container's secondary heat transfer block (102) through the primary cold head (202) and the secondary cold head (203), and finally the magnet is cooled to the working temperature.

9. The method for using the cold head container according to claim 8, characterized in that: The cold head container is installed in a superconducting magnetic resonance device, including fixing and sealing an upper flange (1011) with a magnet outer cylinder (3), fixing an end of a flexible cold conduction plate (105) with a magnet cold shield (4), and fixing a bottom end of a container secondary heat transfer block (102) with a magnet coil skeleton (5).

10. The method for using the cold head container according to claim 8, characterized in that: The vacuum degree of the cold head container is less than 5Pa.

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