Method and device for accurately adjusting excitation power supply system of complex superconducting magnet

Abstract

The invention discloses a method and a device for accurately adjusting an excitation power supply system of a complex superconducting magnet, and the device comprises an upper annular main coil and a lower annular main coil which are symmetrically distributed along the central plane of an accelerator, a plurality of limit rings which are uniformly distributed in the circumferential direction in each annular main coil, and a plurality of shimming coils which are distributed in each limit ring from a small radius to a large radius, the main circuit loop flows through the main coil; the main current loop flows through the limit coil and the shimming coil; the main current loop provides basic running current for the main coil, each limit circle and the shimming coil, each branch circuit of the branch current loop is provided with an independent fine tuning power supply, and the independent fine tuning power supply performs fine tuning on the current of the limit circle and the shimming coil in each branch circuit; the method comprises the following steps: supplying power to all serially connected superconducting coils by using a main loop power supply; the fine tuning power supply independently adjusts the superconducting coil on each branch; independent adjustment of coil current can be realized only by increasing a small amount of thermal load.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-temperature superconducting cyclotron accelerators, and in particular relates to a method and device for accurately adjusting an excitation power supply system of a complex superconducting magnet. Background Art

[0002] Isochronism is one of the important indicators to measure the performance of a cyclotron. In an accelerator with good isochronism, the frequency of the particles rotating in the accelerator is consistent with the high-frequency frequency, ensuring that the particles are accelerated at the voltage peak each time they pass through the high-frequency cavity accelerator gap. The particles can reach the extraction position after fewer turns, reducing the beam loss in the accelerator. Generally speaking, when the magnet of a cyclotron is initially built, the magnetic field cannot meet isochronism, and the magnetic field needs to be corrected through magnet processing and shimming.

[0003] The commonly used methods for magnetic field shimming in room temperature magnet cyclotron accelerators are: (1) strip processing, that is, installing removable strips on the side of the pole and processing the strip width to compensate the magnetic field; (2) sticking blocks on the side of the pole, that is, sticking rectangular blocks of different widths on the side of the magnet to correct the magnetic field.

[0004] Most superconducting cyclotron accelerators in the world use adjusting coils and adjusting rods to compensate for the magnetic field, while some also use conventional accelerator magnet processing to compensate for the magnetic field.

[0005] In a compact high-temperature superconducting cyclotron accelerator, the accelerator size has been reduced to the limit, and it is difficult to have space to install magnetic field adjustment rods. If conventional magnet processing methods are used to fill the gaps, the weight and size of the accelerator will increase significantly, which goes against the original intention of a compact superconducting accelerator.

[0006] The problem with using an adjustment coil is that if an ordinary electromagnet coil is used, the adjustment range is limited due to the heat generated by the coil under vacuum. If a superconducting coil is used, due to structural problems with existing high-temperature superconducting coils, the utilization rate of the superconducting coil will be low, increasing the cost of superconducting materials, or the current of the superconducting coil will be too large, increasing the cost of the low-temperature system and making it difficult to manufacture. Summary of the invention

[0007] In view of the shortcomings of the prior art, a method and device for precise adjustment of the excitation power supply system of a complex superconducting magnet are proposed, with the purpose of solving the problems that if an ordinary electromagnet coil solution is adopted in the prior art, the adjustment range is limited due to the heating of the coil under vacuum; if a superconducting coil solution is adopted, due to the structural problems of the existing high-temperature superconducting coil, the utilization rate of the superconducting coil will be low, the cost of superconducting materials will increase, or the current of the superconducting coil will be too large, which will increase the cost of the cryogenic system.

[0008] The present invention proposes the following technical solutions to solve the problems existing in the prior art:

[0009] A precise regulating device for the excitation power supply system of a complex superconducting magnet is characterized in that: the regulating device comprises two layers of annular main coils arranged symmetrically along the central plane of the accelerator, multiple circumferentially uniformly arranged magnetic pole coils in each layer of annular main coils, multiple shimming coils arranged from small radius to large radius in each layer of main coils, and a main circuit loop flowing through the main coils, a main current loop flowing through the magnetic pole coils and the shimming coils, and multiple branch current loops; the main current loop provides basic operating current for the main coil, each magnetic pole coil and the shimming coil, and each branch of the branch current loop is provided with an independent fine-tuning power supply, which fine-tunes the current of the magnetic pole coil and the shimming coil in the respective branch; the current of each magnetic pole coil and the shimming coil = the current of the main current loop + the current of the fine-tuning power supply branch loop; all the main coils, magnetic pole coils and shimming coils of the device are inside a cryostat, and the main power supply and the fine-tuning power supply are outside the cryostat.

[0010] Furthermore, the branch current loop is composed of two layers of shimming coils with the same radius symmetrically arranged on both sides of the accelerator center plane as a branch, each branch is provided with an independent fine-tuning power supply, and the independent fine-tuning power supply fine-tunes the shimming coil current on the branch; the two layers of shimming coils with the same radius refer to the two layers of shimming coils with the same radius from the center point of the accelerator.

[0011] Furthermore, the branch current loop is composed of all the magnetic pole coils symmetrically arranged on both sides of the accelerator center plane as one branch, and each branch is provided with an independent fine-tuning power supply, which fine-tunes the magnetic pole coil current on the branch.

[0012] Furthermore, the main coil, the pole coil, the shim coil, the main circuit low-temperature end current lead and the fine-tuning circuit low-temperature end current lead are arranged inside the 70K cold screen; the main circuit high-temperature end copper lead R5 and the fine-tuning circuit high-temperature end copper lead R2 are between the 70K screen and the 300K casing, the main circuit external power supply cable resistance is R6, and the fine-tuning circuit external power supply cable resistance is R1.

[0013] Furthermore, the amperage of the main circuit loop is several dozen times the amperage of the branch current loop.

[0014] Furthermore, when the current of the main circuit loop needs to reach a level of 300A, the current of the branch current loop only needs to be less than 10A to meet the magnetic field regulation requirement.

[0015] Furthermore, when the independent fine-tuning power supply fine-tunes the current of the pole coil and the shimming coil in the branch, the adjustment is reversible, and the fine-tuning power supply can adjust the current from large to small, and can also adjust the current from small to large.

[0016] Furthermore, when the independent fine-tuning power supply fine-tunes the current of the pole coil and the shimming coil in the branch, it is an online adjustment.

[0017] A magnetic field adjustment method for a high-temperature superconducting cyclotron, characterized in that:

[0018] Step 1: After the system has finished cooling down, the main circuit power supply is used to supply power to all the superconducting coils connected in series; the superconducting coils connected in series include all the main coils, magnetic limit coils and shimming coils connected in series;

[0019] Step 2: After the power supply current is stable, the fine-tuning power supply of the superconducting coil on each branch is independently adjusted so that the current of the superconducting coil on each branch reaches the designed value; wherein the coils of all fine-tuning loops are independently powered to achieve the purpose of independently adjusting the coil current;

[0020] Step 3: perform magnetic field measurement, and adjust the fine-tuning power supply current of each superconducting coil on each branch according to the magnetic field measurement result, so that the magnetic field meets the accelerator isochronism requirement;

[0021] Step 4: Check whether the current magnetic field meets the accelerator isochronism requirement. If it does not meet the accelerator isochronism requirement, return to step 2. If it meets the accelerator isochronism requirement, end the magnetic field adjustment of the high-temperature superconducting cyclotron.

[0022] Advantages and effects of the present invention

[0023] The present invention utilizes the existing coil structure and independently fine-tunes the current of the superconducting coil by fine-tuning the power supply to achieve the purpose of isochronous regulation of the magnetic field. It has the following effects:

[0024] 1) The present invention realizes isochronous regulation of the magnetic field without increasing the number of coils or the amount of magnetic materials, does not occupy valuable central area space, and has a simple mechanical structure.

[0025] 2) The coil current of the present invention adopts the scheme of main current + fine-tuning current, so that the independent adjustment of the coil current can be achieved by only adding a small amount of heat load.

[0026] 3) The traditional magnetic field regulation by cutting ferromagnetic materials is irreversible, while the present invention adjusts the magnetic field by changing the current, which is reversible.

[0027] 5. Traditional adjustment requires disassembly and assembly and cannot be performed online. The present invention can achieve online adjustment, thereby improving the debugging efficiency of the accelerator.

[0028] 6. Compared with all coils being powered independently, the present invention reduces the power of most power supplies (originally all power supplies required 300A*10V, now only one 300A*10V is needed, and the rest 10A*5V can meet the demand), and reduces the stability requirements for most power supplies (originally all power supplies needed to reach 10ppm stability, now only one needs 10ppm, and the rest only need 100ppm stability). It can greatly reduce the procurement cost of power supplies. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a circuit diagram of a magnetic field regulating device for a high-temperature superconducting cyclotron accelerator of the present invention;

[0030] Figure 2 This is the first viewing angle of the positions of the main coil, magnetic limit circle, and shimming coil on both sides of the center plane of the present invention;

[0031] Figure 3 The second viewing angle of the main coil, magnetic limit circle, and shimming coil positions on both sides of the center plane of the present invention;

[0032] Figure 4 The circuit diagram is optimized for the present invention after considering the resistance on the wire. DETAILED DESCRIPTION

[0033] Design principle of the present invention:

[0034] 1. Innovation of the present invention: The innovation lies in that the magnetic field regulation adopts the scheme of main current + fine-tuning current, so that the independent regulation of coil current can be achieved by only adding a small amount of heat load:

[0035] The first problem solved: the main current + fine-tuning current solution solves the problem that when the superconducting coil solution is used to adjust the magnetic field, the current of the superconducting coil current lead wire is too large, which increases the cost of the cryogenic system. In this embodiment, the main current ampere is 30 times the ampere of the fine-tuning current, and the ampere of the fine-tuning current is one-thirtieth of the ampere of the main current. Since the fine-tuning current is only one-thirtieth of the main current, for each coil, only one-thirtieth of the original heat load is increased to achieve independent regulation of the coil current, thus solving the problem of excessive increase in the heat load of the cryogenic system due to independent regulation of the superconducting coil current.

[0036] The second problem to be solved is that the magnetic field adjustment by cutting of ferromagnetic materials is an irreversible adjustment, which means that the shimming strips can only be cut and not added during the process of digging and repairing (the material of each batch of strips is not exactly the same, and sticking two different materials together will affect the uniformity of the magnetic field.), therefore, a small amount must be cut each time, and once too much is cut, the entire strip will be scrapped. Based on this irreversible magnetic field shimming, the cycle is long and the labor cost is high. The present invention adopts online adjustment and reversible adjustment to effectively improve the work efficiency.

[0037] 2. Difficulty in the design of the present invention: The difficulty lies in ensuring the density of the magnetic field shimming and solving the problem of excessive heat load of the low-temperature system caused by too many current leads of the shimming coils. The density of the magnetic field shimming is to ensure that the number of shimming coils from the small radius to the large radius of each magnetic limit circle is sufficient. If the shimming coils are sparsely spaced, the density of the shimming is poor, resulting in the magnetic field not being properly padded in places where there are no shimming coils. However, when the density of the shimming coils increases, the number of current leads introduced also increases. If the main circuit current is passed through each shimming coil, the heat load of the low-temperature system is also multiplied based on the main circuit. As a result, the cost of maintaining a low-temperature environment is too high. The low-temperature environment is a cold screen environment below 70K. Since the main coil, magnetic pole coil, shimming coil, main circuit current lead and fine-tuning circuit, their low-temperature end current leads are all arranged inside the 70K cold screen, when the current on the shimming coil in the 70K cold screen is overheated, the cooling cost of the 70K cold screen must be increased to maintain a temperature below 70K.

[0038] 3. The solution of the present invention: all the main coils, pole coils and shimming coils are connected in series. The effect of the series connection is that the main circuit flows through the pole coils and shimming coils on each branch circuit, that is, the main coils, pole coils and shimming coils share a main circuit current. Assuming that there are 8 (one group) magnetic limit circles and 56 (7 groups) shimming coils in the upper and lower layers of the main coils, according to the conventional method, 9 main circuit current leads are required. After adopting the method of the present invention, only one main circuit current lead and 8 main circuit current leads of a few tenths are required. At the same time, an independent fine-tuning circuit is added to all the pole coils and shimming coils. The current of the fine-tuning circuit is only a few tenths of the main circuit, which can meet the difference of the magnetic field shimming. And the current of the superconducting coil of the fine-tuning circuit adopts the scheme of main current + fine-tuning current. Although the current of the fine-tuning circuit itself is only a few tenths of the main circuit, the superconducting coil simultaneously accepts the superposition of the main circuit current and the fine-tuning circuit current, so it can ensure normal operation.

[0039] Based on the above principles, the present invention designs a precise adjustment device for the excitation power supply system of a complex superconducting magnet, such as Figure 1-3As shown, its characteristics are: the regulating device includes two layers of annular main coils arranged symmetrically along the central plane of the accelerator, multiple circumferentially uniformly arranged pole coils in each layer of annular main coils, multiple shimming coils arranged from small radius to large radius in each layer of main coils, and a main circuit loop flowing through the main coils, a main current loop flowing through the pole coils and the shimming coils, and multiple branch current loops; the main current loop provides basic operating current for the main coil, each pole coil and the shimming coil, and each branch of the branch current loop is provided with an independent fine-tuning power supply, and the independent fine-tuning power supply fine-tunes the current of the pole coil and the shimming coil in the respective branch; the current of each pole coil and the shimming coil = the main current loop current + the fine-tuning power supply branch loop current; all the main coils, pole coils and shimming coils of the device are inside the cryostat, and the main power supply and the fine-tuning power supply are outside the cryostat.

[0040] like Figure 1 As shown, the branch current loop is composed of two layers of shimming coils with the same radius symmetrically arranged on both sides of the central plane of the accelerator as a branch, and each branch is provided with an independent fine-tuning power supply, which fine-tunes the shimming coil current on the branch; the two layers of shimming coils with the same radius refer to the two layers of shimming coils with the same radius from the center point of the accelerator.

[0041] like Figure 1 As shown, the branch current loop is composed of all the magnetic pole coils symmetrically arranged on both sides of the accelerator center plane as a branch, and each branch is provided with an independent fine-tuning power supply, which fine-tunes the magnetic pole coil current on the branch.

[0042] Supplementary Note 1:

[0043] A. Figure 1 As shown, the center plane of the accelerator is Figure 1 The center plane of the magnet in

[0044] B. Figure 1 There are two types of branches in the circuit. The one on the left is the pole coil branch; the one in the middle and on the right is the shim coil branch.

[0045] C. The pole coil branch consists of four pole coils on the upper layer and four pole coils on the lower layer, a total of eight pole coils together forming a branch;

[0046] D. The shimming coil branch is composed of two layers of shimming coils on the circumference of the same radius as the upper and lower layers, which is a branch. The shimming coils of the same radius as the upper and lower layers are seven groups from small radius to large radius, forming seven shimming coil branches. The seven shimming coil branches include four inside each pole coil and three between the pole coils. Figure 2 shown.

[0047] like Figure 1 , Figure 4 As shown, the main coil, pole coil, shim coil, main circuit low temperature end current lead and fine tuning circuit low temperature end current lead are arranged inside the 70K cold screen; the main circuit high temperature end copper lead R5 and the fine tuning circuit high temperature end copper lead R2 are between the 70K screen and the 300K casing, the main circuit external power supply cable resistance is R6, and the fine tuning circuit external power supply cable resistance is R1.

[0048] The ampere of the main circuit loop is several dozen times the ampere of the branch current loop.

[0049] When the current of the main circuit loop needs to reach 300A, the current of the branch current loop only needs less than 10A to meet the magnetic field regulation requirements.

[0050] When the independent fine-tuning power supply fine-tunes the current of the pole coil and the shimming coil in the branch, the adjustment is reversible. The fine-tuning power supply can adjust the current from large to small, and can also adjust the current from small to large.

[0051] When the independent fine-tuning power supply fine-tunes the current of the pole coil and the shimming coil in the branch, it is an online adjustment.

[0052] A magnetic field adjustment method for a high-temperature superconducting cyclotron, characterized in that:

[0053] Step 1: After the system has finished cooling down, the main circuit power supply is used to supply power to all the superconducting coils connected in series; the superconducting coils connected in series include all the main coils, magnetic limit coils and shimming coils connected in series;

[0054] Step 2: After the power supply current is stable, the fine-tuning power supply of the superconducting coil on each branch is independently adjusted so that the current of the superconducting coil on each branch reaches the designed value; wherein the coils of all fine-tuning loops are independently powered to achieve the purpose of independently adjusting the coil current;

[0055] Step 3: perform magnetic field measurement, and adjust the fine-tuning power supply current of each superconducting coil on each branch according to the magnetic field measurement result, so that the magnetic field meets the accelerator isochronism requirement;

[0056] Supplementary Note 2:

[0057] like Figure 2 As shown, the embodiment of the present invention has eight branches, seven shimming coil branches and one magnetic pole coil branch. The seven shimming coil branches are four inside each magnetic pole coil and three between magnetic pole coils.

[0058] Step 4: Check whether the current magnetic field meets the accelerator isochronism requirement. If it does not meet the accelerator isochronism requirement, return to step 2. If it meets the accelerator isochronism requirement, end the magnetic field adjustment of the high-temperature superconducting cyclotron.

[0059] It should be emphasized that the above specific embodiments are merely explanations of the present invention, and they are not limitations of the present invention. After reading this specification, those skilled in the art can make modifications to the above embodiments without creative contribution as needed, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A precise adjustment device for the excitation power supply system of a complex superconducting magnet. Features: The regulating device comprises two layers of annular main coils arranged symmetrically along the central plane of the accelerator, a plurality of circumferentially uniformly arranged magnetic pole coils in each layer of annular main coils, a plurality of shimming coils arranged from small radius to large radius in each layer of main coils, a main circuit loop flowing through the main coils, a main current loop flowing through the magnetic pole coils and the shimming coils, and a plurality of branch current loops; the main current loop provides basic operating current for the main coil, each magnetic pole coil and the shimming coil, and each branch of the branch current loop is provided with an independent fine-tuning power supply, which fine-tunes the current of the magnetic pole coil and the shimming coil in the respective branch; the current of each magnetic pole coil and the shimming coil = the current of the main current loop + the current of the fine-tuning power supply branch loop; all the main coils, magnetic pole coils and shimming coils of the device are inside the cryostat, and the main power supply and the fine-tuning power supply are outside the cryostat.

2. According to claim 1, a precise adjustment device for the excitation power supply system of a complex superconducting magnet, Features: The branch current loop is composed of two layers of shimming coils with the same radius symmetrically arranged on both sides of the accelerator center plane as a branch, and each branch is provided with an independent fine-tuning power supply, which fine-tunes the shimming coil current on the branch; the two layers of shimming coils with the same radius refer to the two layers of shimming coils with the same radius from the center point of the accelerator.

3. According to claim 1, a precise adjustment device for the excitation power supply system of a complex superconducting magnet, Features: The branch current loop is composed of all the magnetic pole coils symmetrically arranged on both sides of the accelerator center plane as a branch, and each branch is provided with an independent fine-tuning power supply, which fine-tunes the magnetic pole coil current on the branch.

4. According to claim 1, a precise adjustment device for the excitation power supply system of a complex superconducting magnet, Features: The main coil, pole coil, shim coil, main circuit low temperature end current lead and fine-tuning circuit low temperature end current lead are arranged inside the 70K cold screen; the main circuit high temperature end copper lead R5 and the fine-tuning circuit high temperature end copper lead R2 are between the 70K screen and the 300K casing, the main circuit external power supply cable resistance is R6, and the fine-tuning circuit external power supply cable resistance is R1.

5. According to claim 1, a precise adjustment device for the excitation power supply system of a complex superconducting magnet, Features: The ampere of the main circuit loop is several dozen times the ampere of the branch current loop.

6. According to claim 5, a precise adjustment device for the excitation power supply system of a complex superconducting magnet, Features: When the current of the main circuit loop needs to reach 300A, the current of the branch current loop only needs less than 10A to meet the magnetic field regulation requirements.

7. According to claim 1, a precise adjustment device for the excitation power supply system of a complex superconducting magnet, Features: When the independent fine-tuning power supply fine-tunes the current of the pole coil and the shimming coil in the branch, the adjustment is reversible. The fine-tuning power supply can adjust the current from large to small, and can also adjust the current from small to large.

8. According to claim 1, a precise adjustment device for the excitation power supply system of a complex superconducting magnet, Features: When the independent fine-tuning power supply fine-tunes the current of the pole coil and the shimming coil in the branch, it is an online adjustment.

9. A method for precisely regulating the excitation power system of a complex superconducting magnet based on the precise regulating device for the excitation power system of a complex superconducting magnet according to any one of claims 1 to 8, Features: Step 1: After the system has finished cooling down, the main circuit power supply is used to supply power to all the superconducting coils connected in series; the superconducting coils connected in series include all the main coils, limit coils and shimming coils connected in series; Step 2: After the power supply current is stable, the fine-tuning power supply of the superconducting coil on each branch is independently adjusted so that the current of the superconducting coil on each branch reaches the designed value; wherein the coils of all fine-tuning loops are independently powered to achieve the purpose of independently adjusting the coil current; Step 3: perform magnetic field measurement, and adjust the fine-tuning power supply current of each superconducting coil on each branch according to the magnetic field measurement result, so that the magnetic field meets the accelerator isochronism requirement; Step 4: Check whether the current magnetic field meets the accelerator isochronism requirement. If it does not meet the accelerator isochronism requirement, return to step 2. If it meets the accelerator isochronism requirement, end the magnetic field adjustment of the high-temperature superconducting cyclotron.

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