A superconducting magnet excitation system and installation method

Abstract

The invention discloses a superconducting magnet excitation system and an installation method, and relates to the technical field of superconducting magnet excitation. The superconducting magnet excitation system comprises a cryogenic container, a superconducting coil, a superconducting switch, a switch heater and a current lead. The cryogenic container is used to contain liquid helium and maintain the low temperature in the cryogenic container. The superconducting coil is arranged inside the cryogenic container and at least partially immersed in the liquid helium. The superconducting switch is connected to the superconducting coil through a superconducting cable. The superconducting switch is located inside the cryogenic container, and the height of the superconducting switch is higher than the liquid surface of the liquid helium. The switch heater is arranged on the superconducting switch to control the opening and closing of the superconducting switch. The current lead is passed through the top of the cryogenic container, and the end of the current lead located inside the cryogenic container is connected in series with the superconducting coil through an inner cable. The superconducting switch is not immersed in liquid helium, and only a small heating power is needed to change the superconducting switch from a superconducting state to a normal state, thereby reducing the consumption of liquid helium and reducing the opening time of the superconducting switch.

Description

Technical Field

[0001] The invention relates to the technical field of superconducting magnet excitation, and in particular to a superconducting magnet excitation system and an installation method. Background Art

[0002] Superconducting magnets immersed in liquid helium, superconducting switches are usually immersed in liquid helium to obtain a more adequate low-temperature environment. When it is excited or demagnetized, the superconducting switch must first be turned on to provide a prerequisite for the excitation or demagnetization of the superconducting coil. In order to turn on the superconducting switch, it is necessary to heat it. Because it is immersed in liquid helium, it is necessary to apply high-power heating to heat the superconducting switch to the open state (also called the quench state), which will inevitably consume a large amount of liquid helium to achieve the full opening state of the superconducting switch during the entire excitation process. This is an uneconomical technical solution for liquid helium, a scarce resource.

[0003] In addition, conventional superconducting magnets soaked in liquid helium usually install two or more superconducting switches in parallel to shunt the current in order to reduce the switch load. However, the use of more superconducting switches increases the consumption of liquid helium during the excitation process. At the same time, for the closed-loop operation of the coil, the problem of uneven current shunting among multiple switches is introduced, which can easily cause AC loss and lead to switch quenching, thereby causing the entire superconducting magnet to quench.

[0004] Therefore, how to at least partially solve the above-mentioned drawbacks in the superconducting switch excitation process is a technical problem that those skilled in the art need to solve at present. Summary of the invention

[0005] The purpose of the present invention is to provide a superconducting magnet excitation system and method to solve the dependence of superconducting switches on liquid helium immersion, reduce the switch liquid helium consumption during excitation, and increase the stability of the magnet closed-loop operation.

[0006] To achieve the above object, the present invention provides a superconducting magnet excitation system, comprising:

[0007] A cryogenic container, used to contain liquid helium and maintain the low temperature inside the cryogenic container;

[0008] A superconducting coil is disposed inside the cryogenic container and at least partially immersed in liquid helium;

[0009] A superconducting switch is connected to the superconducting coil via a superconducting cable, and the superconducting switch is located inside the cryogenic container, and the height of the superconducting switch is higher than the liquid level of liquid helium;

[0010] A switch heater is arranged on the superconducting switch to control the opening and closing of the superconducting switch;

[0011] The current lead is passed through the top of the cryogenic container, and the end of the current lead located inside the cryogenic container is connected in series with the superconducting coil through an inner cable.

[0012] Preferably, a cooling device is further provided on the cryogenic container, the cooling device comprising a cold head extending into the interior of the cryogenic container, the cold head being used to cool the liquid helium evaporated to a gaseous state, and the superconducting switch is located on a side of the current lead away from the cold head.

[0013] Preferably, two ends of the superconducting switch are connected with superconducting joints, and the superconducting cable and the inner cable are both connected to the corresponding superconducting joints so that the superconducting cable and the inner cable are connected.

[0014] Preferably, a connection base is provided at one end of the inner cable away from the superconducting joint;

[0015] The current leads include a negative current lead and a positive current lead which are arranged at intervals. The negative current lead and the positive current lead are connected to different connection bases to excite or demagnetize the superconducting coil.

[0016] Preferably, a flow channel is provided inside the current lead for allowing the liquid helium that has evaporated into a gaseous state to flow to the outside of the cryogenic container.

[0017] Preferably, there are multiple superconducting coils, and the multiple superconducting coils are symmetrically wound on the coil frame, and all the superconducting coils are connected in series.

[0018] Preferably, the superconducting coil is provided with a thermometer for measuring the temperature thereof.

[0019] Preferably, a fixing piece is provided on the inner wall of the cryogenic container, and one end of the fixing piece facing away from the inner wall of the cryogenic container is connected to the superconducting switch, so that the superconducting switch is suspended inside the cryogenic container.

[0020] A method for installing a superconducting magnet excitation system, applicable to the above-mentioned superconducting magnet excitation system, comprising:

[0021] The superconducting coils are arranged in a cryogenic container, and all the superconducting coils are connected in series;

[0022] A superconducting switch equipped with a switch heater is suspended in the upper part of the cryogenic container through a fixing member, and connected to the superconducting coil through a superconducting cable;

[0023] Connect the connection base in series with the superconducting coil via an inner cable, and connect the current lead to the connection base;

[0024] Liquid helium is added into the cryogenic container, the superconducting coil is at least partially immersed in the liquid helium, and the superconducting switch is located at a height higher than the liquid level of the liquid helium.

[0025] Preferably, the step of suspending the superconducting switch equipped with the switch heater at the upper part of the low-temperature container through a fixing member and connecting it to the superconducting coil through a superconducting cable includes:

[0026] The superconducting switch is installed at a position away from the cold head inside the cryogenic container and is connected to the superconducting coil through a superconducting cable.

[0027] Compared with the above background technology, the superconducting magnet excitation system provided by the present invention has the following beneficial effects:

[0028] 1. The current lead excites the superconducting coil, and the superconducting switch needs to be heated by the switch heater to open the superconducting switch. The superconducting switch is arranged inside the cryogenic container, and the height of the superconducting switch is higher than the liquid level of liquid helium. The superconducting switch is not immersed in liquid helium. Only a small heating power is needed to change the superconducting switch from the superconducting state to the normal state, that is, from the closed state to the open mode, thereby reducing the consumption of liquid helium and shortening the opening time of the superconducting switch;

[0029] 2. The design of using a single superconducting switch not only increases the stability of the closed-loop operation of the superconducting magnet, but also reduces the cost of using the superconducting switch and the cost of liquid helium. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0031] FIG1 is a schematic structural diagram of a superconducting magnet excitation system provided in an embodiment of the present invention;

[0032] FIG. 2 is a partial enlarged view of FIG. 1 .

[0033] in:

[0034] 100-cryogenic container, 110-liquid helium, 120-helium gas;

[0035] 200-superconducting coil, 210-coil frame;

[0036] 300-superconducting switch, 310-superconducting cable, 320-superconducting joint;

[0037] 400 - current lead, 410 - inner cable, 411 - connection base, 420 - negative current lead, 430 - positive current lead. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in 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.

[0039] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0040] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by terms such as “upper”, “lower”, “front”, “backward”, “left” and “right” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the positions or elements referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, they should not be understood as limitations of the present invention.

[0041] The purpose of the present invention is to provide a superconducting magnet excitation system and method to solve the dependence of superconducting switches on liquid helium immersion, reduce the switch liquid helium consumption during excitation, and increase the stability of the magnet closed-loop operation.

[0042] Please refer to FIG. 1 and FIG. 2 . To achieve the above-mentioned purpose, the present invention provides a superconducting magnet excitation system, including a cryogenic container 100 , a superconducting coil 200 , a superconducting switch 300 , a switch heater and a current lead 400 .

[0043] The cryogenic container 100 is used to contain liquid helium 110 and maintain the low temperature inside the cryogenic container 100; the cryogenic container 100 is a multi-layer container, and needs to be able to maintain the liquid helium 110 inside it at a low temperature to prevent external heat from being transferred to the inside of the cryogenic container 100. The upper part of the cryogenic container 100 is provided with a neck tube with a narrower end, and the uppermost end of the neck tube is the outlet of the cryogenic container 100. A safety exhaust port is provided on one side of the neck tube for discharging cold helium gas 120 evaporated from the liquid helium 110 in the cryogenic container 100 to maintain the pressure inside the low temperature holding container.

[0044] The superconducting coil 200 is disposed inside the cryogenic container 100 and at least partially immersed in liquid helium 110 . The liquid helium 110 is used to maintain the temperature of the superconducting coil 200 within a certain range.

[0045] The superconducting switch 300 is connected to the superconducting coil 200 via a superconducting cable 310 . The superconducting switch 300 is located inside the cryogenic container 100 , and the height of the superconducting switch 300 is higher than the liquid level of the liquid helium 110 .

[0046] It should be noted that, in the present embodiment, the number of superconducting switches 300 is set to one, and the height of the superconducting switch 300 is higher than the liquid surface of the liquid helium 110, and does not need to be immersed in the liquid helium 110, and can be arranged in the cold helium gas 120 in the top space of the cryogenic container 100. The steady-state closed-loop operation of the superconducting magnet is realized by a single superconducting switch 300. Before excitation, the superconducting switch 300 that has been fully cooled by the helium gas 120 needs to be heated by the switch heater to be opened. Because the specific heat capacity and convection heat transfer coefficient of the cold helium gas 120 are much smaller than those of the liquid helium 110, only a small heating power (such as 0.1-0.5W) is required to allow the superconducting switch 300 to be quickly opened.

[0047] The amount of liquid helium 110 consumed by the smaller heating power is greatly reduced, and the amount of hot helium 120 generated is relatively small, so the thermal disturbance to the superconducting coil 200 is reduced. When the superconducting coil 200 has been excited to the preset operating current value, the heating of the superconducting switch 300 is stopped. Since the temperature of the cold helium 120 is still around 4.2K, the superconducting switch 300 can be quickly cooled to a superconducting state, and then a closed-loop operation of the superconducting coil 200 and the superconducting switch 300 is formed, which can avoid the situation where the operating current carrying capacity of multiple superconducting switches 300 used in parallel is uneven, thereby avoiding the superconducting switch 300 from being overheated instantaneously and causing the entire superconducting magnet to be quenched.

[0048] The switch heater is provided at the superconducting switch 300 to control the opening and closing of the superconducting switch 300 ; the switch heater controls the temperature of the superconducting switch 300 by working or stopping working, and the temperature of the superconducting switch 300 controls the opening and closing of the superconducting switch 300 , thereby determining the state of the superconducting coil 200 .

[0049] The current lead 400 is passed through the top of the cryogenic container 100 , and the current lead 400 includes a first end located outside the cryogenic container 100 and a second end located inside the cryogenic container 100 . The end (second end) of the current lead 400 located inside the cryogenic container 100 is connected in series with the superconducting coil 200 through an inner cable 410 .

[0050] There are two current leads 400, namely a positive current lead 430 and a negative current lead 420 which are arranged at intervals. The positive current lead 430 and the negative current lead 420 are respectively connected in series with the loop formed by the superconducting coil 200 through the inner cable 410, and are used for charging when the superconducting coil 200 is excited and discharging when the superconducting coil 200 is demagnetized. The positive current lead 430 and the negative current lead 420 are preferably arranged at the above-mentioned neck tube.

[0051] The current lead 400 excites the superconducting coil 200, and the superconducting switch 300 needs to be heated by a switch heater to open the superconducting switch 300. The superconducting switch 300 is arranged inside the low-temperature container 100, and the height of the superconducting switch 300 is higher than the liquid surface of the liquid helium 110. The superconducting switch 300 is not immersed in the liquid helium 110. Only a small heating power is required to change the superconducting switch 300 from the superconducting state to the normal state, that is, from the closed state to the open mode, thereby reducing the consumption of liquid helium 110 and reducing the opening time of the superconducting switch 300. At the same time, the design of using a single superconducting switch 300 not only increases the stability of the closed-loop operation of the superconducting magnet, but also reduces the use cost of the superconducting switch 300 and the cost of liquid helium 110.

[0052] It is understandable that a cooling device is also provided on the cryogenic container 100, and the cooling device includes a cold head extending into the interior of the cryogenic container 100, and the cold head is used to cool the liquid helium 110 that has evaporated to a gaseous state. The superconducting switch 300 is located on the side of the current lead 400 away from the cold head.

[0053] By arranging the position of the superconducting switch 300 to be far away from the cold head, the influence of thermal disturbance on the stability of the superconducting switch 300 when the cold head is shut down is prevented.

[0054] In this embodiment, superconducting joints 320 are connected to both ends of the superconducting switch 300 , and the superconducting cable 310 and the inner cable 410 are both connected to the corresponding superconducting joints 320 , so that the superconducting cable 310 and the inner cable 410 are in communication.

[0055] It should be noted that the inner cable 410 includes an inner positive cable and an inner negative cable, the two ends of the inner positive cable are respectively connected to the positive current lead 430 and a superconducting joint 320, and the two ends of the inner negative cable are respectively connected to the negative current lead 420 and another superconducting joint 320.

[0056] Among them, considering that the positive current lead 430 and the negative current lead 420 are only used when the superconducting coil 200 is excited or demagnetized, in order to facilitate the installation and removal of the positive current lead 430 and the negative current lead 420, a connecting base 411 is provided at the end of the inner cable 410 away from the superconducting joint 320, and the negative current lead 420 and the positive current lead 430 are connected to different connecting bases 411 to excite or demagnetize the superconducting coil 200.

[0057] Taking into account that the current lead 400 will also generate heat when exciting or demagnetizing the superconducting coil 200, a flow channel is provided inside the current lead 400 for the liquid helium 110 that has evaporated to a gaseous state to flow to the outside of the cryogenic container 100. The current lead 400 can be cooled by the flow of the liquid helium 110 to avoid excessive temperature rise of the current lead 400.

[0058] In this embodiment, there are multiple superconducting coils 200, and the multiple superconducting coils 200 are symmetrically wound on the coil frame 210, all the superconducting coils 200 are connected in series, and the ends of the two superconducting cables 310 connected to the superconducting joint 320 away from the superconducting joint 320 are connected to the two superconducting coils 200 located on the outermost side.

[0059] The superconducting coil 200 is provided with a thermometer for measuring its temperature. The thermometer can be provided to intuitively and clearly judge the temperature of the superconducting coil 200, and then perform adaptive processing.

[0060] In order to fix the position of the superconducting switch 300 after installation, a fixing piece is provided on the inner wall of the cryogenic container 100 , and one end of the fixing piece away from the inner wall of the cryogenic container 100 is connected to the superconducting switch 300 , so that the superconducting switch 300 is suspended inside the cryogenic container 100 .

[0061] The present embodiment provides an installation method of a superconducting magnet excitation system, which is applicable to the above-mentioned superconducting magnet excitation system, including arranging a superconducting coil 200 in a cryogenic container 100, and connecting all the superconducting coils 200 in series; suspending a superconducting switch 300 equipped with a switch heater in the upper part of the cryogenic container 100 through a fixing member, and connecting the superconducting coil 200 through a superconducting cable 310; connecting a connecting base 411 in series with the superconducting coil 200 through an inner cable 410, and connecting a current lead 400 to the connecting base 411; adding liquid helium 110 into the cryogenic container 100, the superconducting coil 200 is at least partially immersed in the liquid helium 110, and the height of the superconducting switch 300 is higher than the liquid level of the liquid helium 110.

[0062] Among them, the step of suspending the superconducting switch 300 equipped with a switch heater at the upper part of the low-temperature container 100 through a fixing part and connecting it to the superconducting coil 200 through a superconducting cable 310 is specifically to install the superconducting switch 300 at a position away from the cold head inside the low-temperature container 100, and connect it to the superconducting coil 200 through the superconducting cable 310.

[0063] It should be noted that the layout of the superconducting switch 300 provided in the present application is particularly suitable for the superconducting switch 300 wound with niobium titanium (NbTi) wire, but is not limited to the superconducting switch 300 wound with niobium titanium (NbTi) wire.

[0064] In summary, the superconducting magnet excitation system, superconducting switch 300 and superconducting joint 320 provided by the present application no longer need to be immersed in liquid helium 110, and can be arranged in the cold helium gas 120 in the top space of the cryogenic container 100. The superconducting switch 300 only needs a small heating power to achieve the transition from the closed state to the open state, and the heating power is much smaller than the traditional superconducting switch 300 mode immersed in liquid helium 110. By setting the superconducting switch 300 at a position away from the cold head, the influence of thermal disturbance on the stability of the superconducting switch 300 when the cold head is shut down is prevented. By forming an excitation closed loop with a single superconducting switch 300 and a superconducting coil 200, the uneven instantaneous current distribution of the superconducting switch 300 caused by the use of more than two superconducting switches 300 can be avoided, thereby avoiding the phenomenon of quenching due to overheating inside the superconducting switch 300 and inducing quenching of the entire superconducting coil 200. Using a single superconducting switch 300 reduces the number of superconducting switches 300 used, thereby reducing the manufacturing cost of the superconducting magnet, and also reduces the amount of liquid helium 110 consumed for heating the superconducting switch 300 during the excitation process.

[0065] It should be noted that, in this specification, relational terms such as first and second are merely used to distinguish one entity from other entities, but do not necessarily require or imply any actual relationship or order between these entities.

[0066] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0067] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core ideas of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the present invention.

Claims

1. A superconducting magnet excitation system, characterized in that: include: A cryogenic container, used to contain liquid helium and maintain the low temperature inside the cryogenic container; a superconducting coil, disposed inside the cryogenic container and at least partially immersed in the liquid helium; A superconducting switch connected to the superconducting coil via a superconducting cable, the superconducting switch being located inside the cryogenic container and at a height higher than the liquid level of the liquid helium; A switch heater, disposed on the superconducting switch, to control the opening and closing of the superconducting switch; A current lead is passed through the top of the cryogenic container, and an end of the current lead located inside the cryogenic container is connected in series with the superconducting coil through an inner cable.

2. The superconducting magnet excitation system according to claim 1, characterized in that: The cryogenic container is also provided with a cooling device, which includes a cold head extending into the interior of the cryogenic container, and the cold head is used to cool the liquid helium that has evaporated to a gaseous state. The superconducting switch is located on a side of the current lead away from the cold head.

3. The superconducting magnet excitation system according to claim 1, characterized in that: Both ends of the superconducting switch are connected with superconducting joints, and the superconducting cable and the inner cable are both connected to the corresponding superconducting joints so that the superconducting cable and the inner cable are connected.

4. The superconducting magnet excitation system according to claim 3, characterized in that: One end of the inner cable away from the superconducting joint is provided with a connection base; The current lead comprises a negative current lead and a positive current lead which are arranged at intervals. The negative current lead and the positive current lead are connected to different connection bases to excite or demagnetize the superconducting coil.

5. The superconducting magnet excitation system according to claim 1, characterized in that: A flow channel is provided inside the current lead for the liquid helium volatilized into a gaseous state to flow to the outside of the cryogenic container.

6. The superconducting magnet excitation system according to claim 1, characterized in that: There are multiple superconducting coils, and the multiple superconducting coils are symmetrically wound on the coil frame, and all the superconducting coils are connected in series.

7. The superconducting magnet excitation system according to claim 1, characterized in that: The superconducting coil is provided with a thermometer for measuring the temperature thereof.

8. The superconducting magnet excitation system according to any one of claims 1 to 7, characterized in that: A fixing piece is provided on the inner wall of the cryogenic container, and one end of the fixing piece away from the inner wall of the cryogenic container is connected to the superconducting switch, so that the superconducting switch is suspended inside the cryogenic container.

9. A method for installing a superconducting magnet excitation system, applicable to the superconducting magnet excitation system according to any one of claims 1 to 8, characterized in that: include: Placing a superconducting coil in the cryogenic container and connecting all the superconducting coils in series; A superconducting switch equipped with a switch heater is suspended in the upper part of the low-temperature container through a fixing member, and connected to the superconducting coil through a superconducting cable; Connecting the connection base in series with the superconducting coil via an inner cable, and connecting the current lead to the connection base; Liquid helium is added into the cryogenic container, the superconducting coil is at least partially immersed in the liquid helium, and the superconducting switch is located at a height higher than the liquid level of the liquid helium.

10. The method for installing a superconducting magnet excitation system according to claim 9, characterized in that: The step of suspending the superconducting switch equipped with the switch heater at the upper part of the low-temperature container through a fixing member and connecting it to the superconducting coil through a superconducting cable includes: The superconducting switch is installed at a position away from the cold head inside the low-temperature container, and is connected to the superconducting coil through the superconducting cable.

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