A high-efficiency and convenient uniformity compensation method for a hollow solenoid

Abstract

The application discloses a kind of for hollow solenoid high efficiency convenient uniformity compensation method, it is related to the field of magnetic confinement nuclear fusion, method includes the following steps: configuration reference long straight solenoid, obtain reference long straight solenoid magnetic field uniform region as first uniform region;Configuration and reference long straight solenoid gauge equal, length smaller short solenoid;With short solenoid axial center surface as center, compensation coil is symmetrically set in the preset coordinate position of short solenoid axial two ends;Record compensation coil axial position coordinate, obtain the magnetic field uniform region after short solenoid setting compensation coil, obtain third uniform region;Contrast third uniform region and the axial length of first uniform region;When third uniform region length is greater than or equal to first uniform region, current compensation coil position is defined as qualified position;The method can meet the condition of 100-500ppm uniformity requirement, solve the problem that solenoid is difficult to consider short size and high uniformity.

Description

Technical Field

[0001] This invention relates to magnetic confinement nuclear fusion, and more specifically to an efficient and convenient method for uniformity compensation in hollow solenoids. Background Technology

[0002] In the field of magnetic confinement fusion, the magnetic field needs to be accurately measured using the principle of electromagnetic induction via a magnetic probe coil. Solenoids with high uniformity are commonly used to calibrate magnetic field generators. Theoretically, based on the Biot-Savart law, the magnetic field inside an infinitely long solenoid is absolutely uniform. However, due to practical limitations such as space constraints, cost control, and load energy consumption, the industry considers solenoids with an aspect ratio of 6 to 10 or higher as long straight solenoids. Long straight solenoids typically provide a large uniformity region with a uniformity of ±0.1%, meeting the requirements for magnetic confinement fusion magnetic field testing and calibration applications. In practical applications, although long straight solenoids offer high magnetic field uniformity, it is necessary to increase the aspect ratio to reduce end effects and improve uniformity. Moreover, long straight solenoids occupy a large volume, making them unsuitable for deployment in limited spaces or platforms.

[0003] More importantly, to meet uniformity requirements, static compensation of solenoids requires additional coil length and winding turns outside the effective area, increasing winding and assembly difficulty. Increased conductor length leads to increased winding resistance and required excitation power, resulting in relatively higher energy consumption and load under the same target magnetic field. Dynamic compensation requires adding a compensation coil in the normal direction, and driving the compensation coil with appropriate current through real-time magnetic field measurement and feedback to the control system, leading to higher structural complexity and failure rate. Under limited installation conditions, directly shortening the solenoid length results in a significant increase in leakage flux at the solenoid end and axial gradient of the magnetic field, rapidly shrinking the uniform area and making it difficult to meet magnetic field calibration requirements. Therefore, it is difficult to simultaneously achieve short dimensions and high uniformity with solenoids. How to reduce solenoid length and system power consumption while ensuring the required uniform magnetic field area and calibration is currently a pressing need. Summary of the Invention

[0004] The purpose of this invention is to provide an efficient and convenient uniformity compensation method for hollow solenoids, in order to improve the problem that solenoids are difficult to balance in terms of both short size and high uniformity while meeting the uniformity requirement of 100-500ppm.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A method for efficient and convenient uniformity compensation of hollow solenoids is disclosed. This method is suitable for optimizing the volume of solenoids and includes the following steps: S100, configuring a reference long straight solenoid and obtaining the magnetic field uniformity region of the reference long straight solenoid as the first uniform region; S200, configuring a short solenoid, wherein the diameter of the short solenoid is equal to the diameter of the reference long straight solenoid, and the length of the short solenoid is less than half of the length of the reference long straight solenoid; S300, taking the axial center plane of the short solenoid as the center, and symmetrically setting the compensation coil at preset axial coordinate positions at both ends of the short solenoid; S400, recording the axial position coordinates of the current compensation coil, obtaining the magnetic field uniformity region of the short solenoid after setting the compensation coil, and obtaining the third uniform region; S500, comparing the axial length of the third uniform region with that of the first uniform region; if the length of the third uniform region is less than that of the first uniform region, adjusting the position coordinates of the compensation coil on the short solenoid according to a preset step size, and re-executing S400; if the length of the third uniform region is greater than or equal to that of the first uniform region, setting the current position of the compensation coil as a qualified position.

[0007] In obtaining the uniform magnetic field region, a preset uniformity condition is set, with the magnetic field amplitude at the axis of a reference long straight solenoid as the reference value; the reference long straight solenoid is discretized into multiple axially arranged circular coils; the magnetic field amplitude generated by the position of the circular coils is obtained as the working value; the magnetic field uniformity value of the working value relative to the reference value is calculated; the magnetic field region in the reference long straight solenoid where the magnetic field uniformity value satisfies the preset uniformity condition is taken as the uniform magnetic field region; the method for obtaining the third uniform region is the same as that for the first uniform region.

[0008] Preferably, before setting the compensation coil on the short solenoid, the following steps are performed: before setting the compensation coil, the magnetic field uniform region of the short solenoid is directly obtained to obtain the second uniform region; and the second uniform region is obtained in the same way as the first uniform region; the second uniform region is used to compare the phase difference state between the first uniform region and the third uniform region.

[0009] Preferably, the short solenoid includes at least two main windings, and the compensation coils are respectively disposed at both ends of the axial direction of each main winding.

[0010] A further technical solution is that the compensation coil has one turn at each end of each layer of the main winding.

[0011] A further technical solution is that the compensation coil is connected in series with the main winding of the short solenoid, and the compensation coil and the main winding of the short solenoid are powered by the same power source.

[0012] Preferably, the preset uniformity condition is that the absolute value of the magnetic field uniformity value is less than or equal to 0.05%, and the corresponding magnetic field deviation is limited to within 500ppm by a preset uniformity threshold.

[0013] Preferably, multiple sampling points are set on the axes of the reference long straight solenoid and the short solenoid, and the axial lengths of the first uniform region and the third uniform region are the lengths of the regions that continuously meet the preset uniformity threshold among the multiple sampling points.

[0014] Compared with the prior art, the beneficial effects of the present invention are at least one of the following:

[0015] This invention uses the uniform magnetic field region of a reference long straight solenoid as the compensation optimization target. While maintaining a consistent solenoid diameter, it reduces the solenoid length, making it more convenient to use. A short solenoid employs a two-layer main winding, forming a compensation winding through symmetrical compensation coils to correct the end magnetic field. This allows for a reduction in the number of turns while maintaining the same winding density and magnetic field amplitude. Simultaneously, a direct comparison between the third and first uniform regions facilitates adjustment of the compensation coil's position coordinates along the short solenoid's axial direction. The position of the compensation coil is then adjusted iteratively to determine the appropriate compensation position by adjusting the end magnetic field attenuation characteristics of the short solenoid. Macroscopically, while the short solenoid's length is reduced, its performance approaches or even surpasses that of the reference long straight solenoid. The inductance and resistance of the short solenoid are reduced to less than 50% of their original values, significantly reducing the power supply's parameter requirements and power consumption, thus saving costs and energy.

[0016] This invention utilizes a short solenoid with two symmetrical main windings and only adds four turns of compensation coil. While ensuring magnetic field amplitude, uniformity, and uniformity region, it avoids overall size increases and the length effects caused by multiple turns or multiple stages of compensation coil. Furthermore, the compensation coil is connected in series with the short solenoid winding and powered by the same power supply, ensuring a deterministic correlation between the compensation coil current and the main winding current. The compensation coil current can change synchronously with the main winding current, eliminating the need for a separate compensation power supply and additional control system. This effectively avoids the impact of compensation state errors caused by current ratio errors, power supply drift, and synchronization control errors. Compared to traditional methods that determine the compensation structure based on local magnetic field changes or empirical parameters, this short solenoid, constrained by the target uniformity region length, can achieve an effective uniformity region comparable to or larger than that of a reference long straight solenoid. It also effectively reduces the design complexity caused by the simultaneous coupling of parameters such as the number of compensation coil turns, compensation current, and the spacing between multiple coil sets.

[0017] In practical applications, the structure of this invention, under the same requirements for magnetic field amplitude, uniformity, and uniform region, can have a smaller volume and use fewer compensation turns compared to traditional long straight solenoids. Products configured using this method can have a compact structure, eliminating the need for complex winding techniques and significantly improving assembly efficiency. The portability advantage of the optimized short solenoid can be greatly expanded into magnetic field calibration applications in the field of nuclear fusion. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process of the present invention.

[0019] Figure 2 This is a diagram showing the ±0.05% uniformity zone distribution and axial uniformity of an uncompensated long solenoid in one embodiment.

[0020] Figure 3 This is a diagram showing the ±0.05% uniformity zone distribution and axial uniformity of an uncompensated short solenoid in one embodiment.

[0021] Figure 4 The diagram shows the distribution of the ±0.05% uniform zone and the schematic diagram of the axial uniformity of the short solenoid after compensation treatment according to the present invention.

[0022] Figure 5 A comparison chart of the axial uniformity (-25% to +10%) of various solenoids.

[0023] Figure 6 A magnified comparison of the high uniformity region (-0.25% to +0.1%) at the center of various solenoids. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this invention are only used to explain the relative positional relationship, movement, etc., in a specific working state. If the specific posture changes, the directional indication will also change accordingly. In this invention, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be an electrical signal connection or a signal connection; it can also refer to the internal connection of two components or the interaction relationship between two components, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0026] If the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0027] In the field of magnetic confinement fusion, the magnetic fields generated by the magnet coils, plasma, and various currents such as induced eddy currents in the magnetic confinement device need to be accurately measured for monitoring the device's basic parameters, real-time plasma control, and evaluation of electromagnetic force loads. For solenoids, having a large homogeneous region under ±0.05% conditions is an important technical indicator to meet the homogeneity requirements of the magnetic confinement fusion field.

[0028] For reference, the design of solenoids involves testing relevant parameters under simulation conditions. The axial magnetic field distribution and uniform region of the reference long straight solenoid are obtained in advance through numerical calculation. Short solenoids and compensation coil schemes are screened before winding, which reduces the workload of repeatedly winding, disassembling and assembling and magnetic field mapping to determine compensation parameters, improves design efficiency and reduces test costs.

[0029] It should be noted that, in addition to ensuring experimental performance, this invention also aims to significantly expand the application scenarios of solenoids in magnetic field calibration testing in the field of magnetic confinement nuclear fusion, making it possible to directly perform in-situ or quasi-in-situ calibration of magnetic sensors within magnetic confinement nuclear fusion devices.

[0030] The term "in-situ" refers to the magnetic sensor being installed without any disassembly or installation, and the magnetic field generator being placed at the sensor's location for use.

[0031] Explanation of the term "quasi-in-situ": A portable magnetic field generator is placed in the vacuum chamber of a magnetic confinement fusion device. The magnetic sensor only needs to be disassembled and calibrated in the vacuum chamber before being reassembled in its original position.

[0032] refer to Figure 1As shown, one embodiment of the present invention is an efficient and convenient uniformity compensation method for hollow solenoids. This method is suitable for optimizing the volume of solenoids and includes the following steps: S100, configuring a reference long straight solenoid, and obtaining a magnetic field uniform region of the reference long straight solenoid as a first uniform region. When obtaining the magnetic field uniform region, a preset uniformity condition is set, and the magnetic field amplitude at the axis of the reference long straight solenoid is obtained as a reference value; the reference long straight solenoid is discretized into multiple axially arranged circular coils; the axial magnetic field distribution of the entire solenoid is obtained by magnetic field superposition, and the difficulty of direct calculation of continuous windings is reduced; the magnetic field amplitude generated at the position of the circular coil is obtained as a working value; the magnetic field uniformity value of the working value relative to the reference value is calculated; the magnetic field region in the reference long straight solenoid where the magnetic field uniformity value satisfies the preset uniformity condition is taken as the magnetic field uniform region.

[0033] The reference long straight solenoid is an existing solenoid, with its length set as L and its diameter set as D. The uniformity of the solenoid under the length L and diameter D is calculated. The principle is based on the Biot-Savart law. The magnetic field distribution of any ring in space is realized through numerical calculation. By vector superposition of the magnetic fields generated by multiple rings, the magnetic field amplitude distribution generated by the solenoid in space can be obtained, and the magnetic field uniformity of its axis can be obtained.

[0034] In magnetic field calibration tests for magnetic confinement fusion, the homogeneity limit is typically set at less than or equal to 500 ppm (≤ ±0.05%). Therefore, this homogeneity condition is preset as the compensation target for the short solenoid. Specifically, the magnetic field amplitude at the axis of the reference long straight solenoid is B0, and the magnetic field amplitude generated by all discrete circular coils of the reference long straight solenoid at the axial sampling position R is B. R Then, when defining the magnetic field uniformity at position R, the formula for calculating uniformity is [(B R -B0) / B0]×100%; Calculate the uniformity of the circular coil at all positions, and take the magnetic field region that satisfies the range of ±0.05% as the first uniform region. The first uniform region is mainly used as the reference for the magnetic field uniformity.

[0035] S200, a short solenoid is configured, wherein the diameter of the short solenoid is equal to the diameter of the reference long straight solenoid, and the length of the short solenoid is less than half the length of the reference long straight solenoid. Alternatively, the diameter of the short solenoid is the same as that of the reference long straight solenoid, and the length of the short solenoid is less than half the length of the reference long straight solenoid.

[0036] By keeping the diameter of the short solenoid consistent with that of the reference long straight solenoid, a comparison can be made between the short solenoid and the reference long straight solenoid without changing the installation channel and radial test space of the object under test. This avoids the influence of magnetic field analysis caused by the difference in diameter. At the same time, in the relatively uniform region, the causes of variables can be better focused on the axial length and the structure of the compensation coil.

[0037] Considering that the reference long straight solenoid has a large aspect ratio to obtain a large uniform region, shortening the short solenoid by making its length less than half that of the reference long straight solenoid can significantly shorten the solenoid and enhance the end effect. Simultaneously, this leads to a deterioration in the magnetic field uniformity in the central region, placing the short solenoid under conditions requiring compensation. This facilitates research into compensation mechanisms for insufficient magnetic field at the ends or axial field distribution distortion in the short solenoid. Furthermore, by gradually optimizing the compensation scheme through differences in magnetic field uniformity within a smaller volume, the magnetic field uniformity can be brought close to or reached that of the reference long straight solenoid.

[0038] S300, taking the axial center plane of the short solenoid as the center, the compensation coil is symmetrically arranged at the preset axial coordinate positions at both ends of the short solenoid.

[0039] In this design, the axis of the solenoid is defined as the Z-axis, and the midpoint between the two end faces of the short solenoid is defined as the origin of the Z-axis. The axial center plane of the short solenoid is a plane located at the origin of the Z-axis and perpendicular to the axis of the solenoid. It should be noted that this axial center plane is usually also the median plane of the effective winding region of the short solenoid along its axial length.

[0040] As an example, a coordinate system is established with the axial direction of the short solenoid as the axial coordinate axis. The midpoint of the effective winding region of the short solenoid along the axial length direction is defined as the axial center plane, and the position of the axial center plane is defined as the origin of the axial coordinate system.

[0041] Considering that the axial magnetic field distribution of the short solenoid is symmetrical about the axial center plane, the compensation coils are symmetrically set at both ends of the short solenoid along the axial direction, so that the compensation magnetic field also maintains the symmetry of the axial center plane, thereby reducing the risk of bias and improving the uniformity of the magnetic field in the central region.

[0042] As an example, if the axial coordinate position of one end of the compensation coil is +A, then the axial coordinate position of the other end of the compensation coil is -A, where A is the axial position parameter of the compensation coil determined according to the axial magnetic field distribution of the short solenoid and the preset uniformity conditions.

[0043] The preset axial coordinate position is usually calculated by measuring the deviation distribution of the axial magnetic field of the short solenoid relative to the reference value. The purpose is to reduce the magnetic field deviation in the central region of the short solenoid and expand the magnetic field region that meets the preset uniformity conditions. The position is selected from the axial coordinate position of the compensation coil or obtained through iteration.

[0044] S400, record the axial position coordinates of the current compensation coil, obtain the magnetic field uniformity region after the compensation coil is set on the short solenoid, and obtain the third uniform region. For reference, the first and third uniform regions use the same reference value definition method. The first uniform region uses the magnetic field amplitude at the axial center of the reference long straight solenoid as the reference value, and the third uniform region uses the magnetic field amplitude at the axial center of the compensated short solenoid as the reference value.

[0045] To ensure comparability between different solenoids, the third uniform region is obtained in the same way as the first uniform region. The magnetic field amplitude at the axial center of the compensated short solenoid is used as the compensation reference value, and the magnetic field amplitude at each axial sampling position of the compensated short solenoid is used as the compensation working value. The magnetic field uniformity value at each axial sampling position is calculated based on the deviation of the compensation working value from the compensation reference value. The continuous magnetic field region whose magnetic field uniformity value meets the preset uniformity condition is designated as the third uniform region. Furthermore, the reference long straight solenoid and the compensated short solenoid use the same uniformity calculation formula, sampling position, and uniformity evaluation conditions.

[0046] S500: Compare the axial lengths of the third uniform zone and the first uniform zone; if the length of the third uniform zone is less than that of the first uniform zone, adjust the position coordinates of the compensation coil on the short solenoid according to the preset step size, and re-execute S400; if the length of the third uniform zone is greater than or equal to that of the first uniform zone, set the current position of the compensation coil as the qualified position.

[0047] Using the first uniform region as a comparison benchmark for the third uniform region can determine the target uniform region length that the short solenoid needs to reach after compensation, clarify the compensation target of the short solenoid, and at the same time, the first uniform region can be used as a comparison object for subsequent compensation coil position iterations.

[0048] For reference, the axial length of the first uniform zone is used as the target compensation length, and the axial length of the third uniform zone is used as the current compensation result length. By comparing the target compensation length and the current compensation result length, in principle, when the axial length of the third uniform zone is greater than or equal to the axial length of the first uniform zone, the axial position coordinates of the current compensation coil can be used as the target compensation position.

[0049] On the one hand, when the axial length of the third uniform zone is less than the axial length of the first uniform zone, the current position of the compensation coil is determined to be an unqualified position. The axial position coordinates of the compensation coil need to be readjusted according to the preset step size, and then S400 is executed again to obtain the adjusted third uniform zone. The first uniform zone is compared again until the axial length of the third uniform zone is greater than or equal to the axial length of the first uniform zone.

[0050] On the one hand, when the axial length of the third uniform zone is equal to the axial length of the first uniform zone, it means that the current compensation result length has reached the compensation target length. The short solenoid after compensation at this position has reached the compensation target. Then the current compensation coil position is set as a qualified position, and the compensated short solenoid can replace the reference long straight solenoid.

[0051] On the one hand, when the axial length of the third uniform zone is greater than the axial length of the first uniform zone, it indicates that the current compensation result length exceeds the compensation target length. The short solenoid after compensation at this position exceeds the compensation target. This position is the preferred compensation position, and the short solenoid after compensation is better than the reference long straight solenoid.

[0052] It is important to note that to confirm whether a position is optimal, the search range can be adjusted by traversing multiple compensation coil positions. Within the preset axial search range, the compensation coils are adjusted sequentially according to a preset step size, and S400 is re-executed after each adjustment to obtain the third uniform region corresponding to different compensation coil positions. The correspondence between the coordinates of each compensation coil position and the axial length of the corresponding third uniform region is recorded. When there is a compensation coil position whose axial length of the third uniform region is greater than or equal to the axial length of the first uniform region, this compensation coil position is taken as a candidate compensation position. The position with the largest axial length of the third uniform region is selected from the candidate compensation positions as the optimized position.

[0053] In principle, all positions are traversed, and only when there is no compensation coil position within the preset axial search range where the axial length of the third uniform zone is greater than or equal to the axial length of the first uniform zone, the compensation coil position with the largest axial length of the third uniform zone is selected as the optimal position.

[0054] Based on the above embodiments, another embodiment of the present invention is that, before the compensation coil is set on the short solenoid, the following steps are performed: before the compensation coil is set, the magnetic field uniform region of the short solenoid is directly obtained to obtain a second uniform region, and the second uniform region is obtained in the same way as the first uniform region.

[0055] Multiple sampling points are set on the axes of both the reference long straight solenoid and the short solenoid. The axial length of the uniform region is the length of the area that continuously meets the preset uniformity threshold among the multiple sampling points. By setting multiple sampling positions on the axes of both the reference long straight solenoid and the short solenoid, the magnetic field uniformity value is calculated point by point, and the area that continuously meets the preset uniformity condition (≤±0.05%) is determined as the magnetic field uniform region.

[0056] The second uniform region is used to compare the phase difference between the first and third uniform regions. Generally, the second uniform region is necessarily inferior to the first uniform region. Before setting the compensation coil, the axial magnetic field distribution of the short solenoid is calculated, and the magnetic field uniform region of the short solenoid in the uncompensated state is obtained as the second uniform region. The second uniform region is used as a reference to reflect the basic uniformity of the short solenoid in the uncompensated state, and is used to compare with the first and third uniform regions. In a more objective way, the uniform region loss of the short solenoid relative to the reference long straight solenoid and the uniform region compensation of the short solenoid by the compensation coil are expressed.

[0057] Based on the above embodiments, another embodiment of the present invention is that the short solenoid includes at least two layers of main windings, and the compensation coils are respectively disposed at both axial ends of each layer of main windings. Specifically, the short solenoid includes at least two layers of main windings arranged radially in sequence, each layer of main windings having a first axial end and a second axial end disposed opposite to each other; and the compensation coils are respectively disposed at the first axial end and the second axial end of each layer of main windings, so that the compensation coils are respectively disposed at both axial ends of each layer of main windings.

[0058] One feasible implementation is that the compensation coil has one turn at each end of each layer of the main winding. By setting the compensation coils at both ends of the axial direction of each layer of the main winding, the compensation coils and the main winding are symmetrical. By setting one turn of compensation coil at each end of each layer, the overall number of compensation turns can be reduced. Furthermore, end compensation is performed for the multi-layer main winding, making the compensation magnetic field more uniform along the radial direction.

[0059] One feasible implementation is to reduce the drift risk and synchronization control difficulty caused by current matching errors from different power sources by connecting the compensation coil in series with the main winding of the short solenoid, and powering both the compensation coil and the main winding of the short solenoid with the same power source.

[0060] On the one hand, after the main winding and the compensation coil are connected in series, they are in the same current loop, and the current flowing through them can remain the same, resulting in high controllability of magnetic field uniformity. Specifically, under a variable current condition, the compensation ratio of the compensation coil to the end magnetic field of the total magnetic field formed by the main winding and the compensation coil remains stable. Macroscopically, this means that when the magnetic field of the main winding changes, the compensation magnetic field also changes by the same proportion, avoiding the problem of the compensation magnetic field being too strong or too weak due to the drift of the compensation current.

[0061] On the one hand, the main winding and the compensation coil are connected in series. Since the current is the same, it not only reduces the need for independent compensation power supply, but also objectively reduces the difficulty of current synchronization control. It avoids the need to add an external current adjustment device, and the system complexity will be significantly reduced. This is especially useful for subsequent repeated experiments and testing under different current intensities, which meets the requirements of calibration consistency and engineering reproducibility.

[0062] Based on the above embodiments, in order to better determine the compensation effect of the compensation coil on the shortened solenoid, another embodiment of the present invention is that the length of the short solenoid is less than half the length of the reference long straight solenoid. After shortening the length by at least half, the end effect of the short solenoid will be significantly enhanced, and the uniform region in the uncompensated state will usually be significantly smaller than that of the reference long straight solenoid, making it easier to express the degree to which the compensation coil compensates for the uniformity loss caused by the shortening.

[0063] At the same time, the short solenoid, with its length reduced by at least half, can be identified as an object with actual compensation needs, thus avoiding the short solenoid being regarded as a miniaturized structure of a benchmark long straight solenoid with similar performance.

[0064] Based on the above embodiments, another embodiment of the present invention is that the preset uniformity condition is that the absolute value of the magnetic field uniformity value is less than or equal to 0.05%, so that the magnetic field uniformity value is within the range of -0.05% to +0.05%. Limited by the preset uniformity threshold, the relative deviation of the magnetic field is required to be controlled within ±500ppm (≤±0.05%) to meet the relevant engineering indicators of magnetic confinement nuclear fusion.

[0065] By setting the uniformity conditions, the region in the reference long straight solenoid that meets ±500ppm (≤±0.05%) can be determined as the first uniform region; similarly, the regions in the uncompensated short solenoid and the short solenoid with compensation coil set can both meet ±500ppm (≤±0.05%) as the second and third uniform regions.

[0066] By limiting the length of the short solenoid to less than half the length of the reference long straight solenoid, and setting the uniformity condition to a region that meets ±500ppm (≤±0.05%), and by searching and filtering the position of the compensation coil, a balance is achieved between optimizing the volume of the short solenoid and restoring the magnetic field uniformity.

[0067] One embodiment of the present invention is based on a uniformity requirement of ±0.05%, and tests and comparisons are conducted using specific parameters. The specific scheme is as follows:

[0068] Scheme 1 is set up, which uses a long straight solenoid without any compensation. The solenoid length is set to L and the diameter to D. Uniformity is calculated, and the ±0.05% uniform region is displayed. The reference long straight solenoid in Scheme 1 has a length of 800 mm, a diameter of 120 mm, an aspect ratio L / D = 6.67, and a winding helix density of 12 mm, with a total of 134 turns in two layers. A 10 ampere current is applied, generating a magnetic field of approximately 20.73 Gauss at the center of the reference long straight solenoid. Then, the distribution of the ±0.05% uniform region and the uniformity value of the axis are calculated. Figure 2 .

[0069] Scheme Two is adopted, which uses a short solenoid without any compensation. The solenoid in Scheme Two has a nominal diameter of 120 mm, a reduced length of 290 mm, an aspect ratio of L / D = 2.4, and maintains a winding helix density of 12 mm, with a total of 50 turns in two layers. Under a current of 10 amperes, the short solenoid in Scheme Two generates a magnetic field of approximately 19.54 Gauss at its center. Then, the distribution of its ±0.05% uniform region and the uniformity of its axis are calculated. Figure 3 .

[0070] Scheme 3 is designed based on Scheme 2, which significantly reduces uniformity and uniformity area. One turn is added at each of the two ends of the short solenoid in Scheme 2 at a suitable symmetrical position, forming a compensation coil with a total of 4 turns added symmetrically in two layers. The compensation coil is connected in series with the circular coil on the short solenoid in Scheme 2, so that the compensation coil is an additional winding of the circular coil. At the same time, its ±0.05% uniformity area is calculated.

[0071] The short solenoid after compensation in Scheme 3 has a design length of 290mm, a nominal diameter of 120mm, and an aspect ratio of L / D=2.4. It maintains a winding helix density of 12mm and a total of 50 turns across two layers. One additional turn is added at each axial position Z of ±67mm. Considering that the short solenoid in Scheme 2 has two main windings, four additional turns are added to each layer. After compensation, the short solenoid in Scheme 3 has a total of 54 turns across two layers. Under the same 10 ampere current condition, a magnetic field of approximately 20.01 Gauss will be generated at the center of the short solenoid in Scheme 3. The distribution of its ±0.05% uniform region and the uniformity of its axis are calculated, yielding... Figure 4 .

[0072] refer to Figures 2 to 4 The length of the solenoid in Scheme 3 is only 290 / 800≈36% of that in Scheme 1. With the bore diameter and winding helix density remaining unchanged, the solenoid in Scheme 3 achieves better uniformity and uniformity zone than Scheme 1 by only increasing the number of windings by 4.

[0073] Further reference Figure 5 Using the same naming method as the aforementioned embodiments, schemes one to three are labeled as ①②③. By scanning with a large step size to cover the entire axis, the curves of the three schemes with uniformity in the range of -25% to +10% are compared.

[0074] At the same time, refer to Figure 6 ( Figure 6 for Figure 5 (Enlarged view of the vertical axis). Considering that the smaller the absolute value of the uniformity value, the closer the magnetic field is to the center and the better the uniformity, the extraction range is in the range of -0.25% to +0.1%. By compressing the range of the vertical axis, an enlarged view of the central highly uniform region is obtained.

[0075] analyze Figure 5 and Figure 6 Scheme 3's solenoid is only 290mm long, but the area with a uniformity of ±0.05% exceeds 130mm in axial length. In contrast, Scheme 1's solenoid is 800mm long, and the area with a uniformity of ±0.05% is 100mm in axial length. Scheme 2, with its short solenoid without compensation, has a uniformity area of ​​less than 20mm, which completely fails to meet the calibration and testing requirements for larger magnetic sensing coils.

[0076] For small magnetic probes with an outer diameter not exceeding Φ50mm and a length not exceeding 100mm in magnetic confinement devices, the short solenoid, after being reduced in volume and compensated using this method, can achieve a magnetic field uniformity better than ±0.05%, meeting high calibration requirements. Furthermore, the magnetic induction intensity generated by the compensated short solenoid is comparable in magnitude to that of a long straight solenoid, thus further confirming the advantages of this method.

[0077] For reference, taking Scheme 3 as an example, using a 20 Gauss, 200Hz alternating magnetic field as the calibration magnetic field, for a magnetic field coil with an area of ​​0.1㎡, the calibration voltage formula can be used to determine ε=S×dB / dt. Since the calibration magnetic field can usually be regarded as a sinusoidal alternating magnetic field, its standard formula for sinusoidal magnetic field is B(t)=B0sin(2πft), then the peak value of the induced electromotive force ε=S×dB / dt=S×B×2πf; where S is the effective area with a value of 0.1㎡; B is the magnetic field value of 20 Gauss (0.002Tesla); and f is the frequency of 200Hz. After substituting the parameters, ε=S×B×2πf≈0.25V. The 0.25V test signal output by the magnetic sensor is sufficient to be accurately measured by a digital multimeter or data acquisition device.

[0078] In this specification, terms such as "one embodiment," "another embodiment," "embodiment," and "preferred embodiment" refer to specific features, structures, or characteristics described in connection with that embodiment, which are included in at least one embodiment described in the general description of this application. The appearance of the same term in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure, or characteristic is described in connection with any embodiment, the intention is to suggest that implementing such a feature, structure, or characteristic in conjunction with other embodiments also falls within the scope of this invention.

[0079] Although the invention has been described herein with reference to several illustrative embodiments, it should be understood that many other modifications and implementations can be devised by those skilled in the art, which will fall within the scope and spirit of the principles disclosed herein. More specifically, various variations and modifications can be made to the components and / or layout of the subject matter arrangement within the scope of the disclosure, drawings, and claims. Besides variations and modifications to the components and / or layout, other uses will be apparent to those skilled in the art.

Claims

1. A highly efficient and convenient uniformity compensation method for hollow solenoids, suitable for optimizing the volume of solenoids, characterized in that, The method includes the following steps: S100, configure a reference long straight solenoid, and obtain the magnetic field uniform region of the reference long straight solenoid as the first uniform region; S200, a short solenoid is configured, wherein the diameter of the short solenoid is equal to the diameter of the reference long straight solenoid, and the length of the short solenoid is less than half of that of the reference long straight solenoid; S300, with the axial center plane of the short solenoid as the center, the compensation coil is symmetrically set at the preset axial coordinate positions at both ends of the short solenoid. S400, record the axial position coordinates of the current compensation coil, obtain the magnetic field uniform region after the short solenoid is set with the compensation coil, and obtain the third uniform region; S500: Compare the axial lengths of the third uniform zone and the first uniform zone; if the length of the third uniform zone is less than that of the first uniform zone, adjust the position coordinates of the compensation coil on the short solenoid according to the preset step size, and re-execute S400; if the length of the third uniform zone is greater than or equal to that of the first uniform zone, set the current position of the compensation coil as the qualified position. In obtaining the uniform magnetic field region, a preset uniformity condition is set, with the magnetic field amplitude at the axis of a reference long straight solenoid as the reference value; the reference long straight solenoid is discretized into multiple axially arranged circular coils; the magnetic field amplitude generated by the position of the circular coils is obtained as the working value; the magnetic field uniformity value of the working value relative to the reference value is calculated; the magnetic field region in the reference long straight solenoid where the magnetic field uniformity value satisfies the preset uniformity condition is taken as the uniform magnetic field region; the method for obtaining the third uniform region is the same as that for the first uniform region.

2. The efficient and convenient uniformity compensation method for hollow solenoids according to claim 1, characterized in that: Before setting the compensation coil on the short solenoid, the following steps are performed: before setting the compensation coil, the magnetic field uniform region of the short solenoid is directly obtained to obtain the second uniform region; and the second uniform region is obtained in the same way as the first uniform region; the second uniform region is used to compare the difference between the first uniform region and the third uniform region.

3. The efficient and convenient uniformity compensation method for hollow solenoids according to claim 1, characterized in that: The short solenoid includes at least two main windings, and the compensation coils are respectively disposed at both ends of the axial direction of each main winding.

4. The efficient and convenient uniformity compensation method for hollow solenoids according to claim 3, characterized in that: The compensation coil has one turn at each end of each layer of the main winding.

5. The efficient and convenient uniformity compensation method for hollow solenoids according to claim 3, characterized in that: The compensation coil is connected in series with the main winding of the short solenoid, and the compensation coil and the main winding of the short solenoid are powered by the same power source.

6. The efficient and convenient uniformity compensation method for hollow solenoids according to claim 1, characterized in that: The preset uniformity condition is that the absolute value of the magnetic field uniformity value is less than or equal to 0.05%, and the corresponding magnetic field deviation is limited to within 500ppm by a preset uniformity threshold.

7. The efficient and convenient uniformity compensation method for hollow solenoids according to claim 1, characterized in that: Multiple sampling points are set on the axes of the reference long straight solenoid and the short solenoid. The axial lengths of the first uniform region and the third uniform region are the lengths of the regions among the multiple sampling points that continuously meet the preset uniformity threshold.

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