A compact spherical tokamak inverse flux measurement system and compensation method

Abstract

The application discloses a compact spherical tokamak inverse magnetic flux measuring system and a compensation method, and belongs to the technical field of magnetic confinement fusion, and the system comprises a concentric double-ring inverse magnetic coil assembly, a coil positioning support assembly, an adjustable weight difference analog integrator, a toroidal field vacuum compensation unit, a poloidal field dynamic compensation unit, an integral drift correction unit and a data acquisition and macroscopic parameter inversion unit. The concentric double-ring inverse magnetic coil assembly comprises an inner-ring magnetic flux coil and an outer-ring magnetic flux coil, and precise installation in a vacuum chamber is realized through the coil positioning support assembly; the adjustable weight difference analog integrator adjusts the weight of the outer-ring signal, compensates for residual error and completes conversion from voltage to inverse magnetic flux; the application solves the technical problems of limited space of a compact spherical tokamak vacuum chamber, difficulty in extracting weak inverse magnetic signals under short-pulse working conditions and large background error interference, realizes high-precision measurement of inverse magnetic flux, and is suitable for the operation characteristics of the compact spherical tokamak.

Description

Technical Field

[0001] This invention relates to the field of magnetic confinement fusion technology, and in particular to a compact spherical tokamak inverse magnetic flux measurement system and compensation method. Background Technology

[0002] In magnetic confinement fusion devices, plasma energy storage, poloidal specific pressure, and energy confinement time are important macroscopic parameters for evaluating discharge confinement performance. Dimagnetic measurement inverts these parameters by detecting changes in the circumferential magnetic flux generated by the plasma. It features non-perturbation, global response, and the ability to be acquired synchronously with other magnetic diagnostic methods. Various engineering solutions have been developed for tokamak devices such as HL-2A, EAST, WEST, KSTAR, ASDEX Upgrade, and JT-60SA. Existing solutions typically employ methods such as single-loop or compensating-loop structures, concentric double-loop differential structures, digital or analog integration, and vacuum background calibration to reduce the influence of applied coil current and vacuum chamber eddy currents on the dimagnetic signal.

[0003] However, existing technologies are primarily geared towards medium to large tokamak operations or longer pulse operation conditions. For compact spherical tokamaks, the limited installation space within the vacuum chamber and the low toroidal diameter ratio result in a strong circumferential magnetic field. Spatial gradients, minute differences in the effective area of ​​the inner and outer loop coils, installation eccentricity, and deformation of the support structure will all be amplified into significant background coupling errors.

[0004] Under short-pulse discharge conditions, the reverse magnetic flux is typically much smaller than the vacuum circumferential magnetic flux; taking the typical NCST operating condition as an example, the circumferential magnetic flux measured by a single reverse magnetic coil is approximately 6 × 10⁻⁶. -2 Wb, while the diamagnetic flux to be measured is approximately 6 × 10⁻⁶. -5 Wb up to 6×10 - 4 Wb. Therefore, the common-mode residue of the circumferential field, the dynamic coupling of the poloidal field, the vacuum chamber wall current / eddy current, the integrator zero-point drift, and the data acquisition noise may all be on the same order of magnitude as the effective signal.

[0005] While existing concentric ring diamagnetic measurement technology can suppress part of the circumferential field background through differential structures, it still has the following shortcomings: First, it relies on the accurate determination of the difference in coil geometric area, and the effective area and position are difficult to reproduce accurately after actual installation; second, it lacks a component calibration and subtraction process for the dynamic coupling of poloidal fields such as ohmic field coils and vertical field coils, which is compatible with the device's operating conditions; third, a longer integration time constant is beneficial for reducing drift but will weaken the response to rapid energy changes in short pulses on the order of hundreds of milliseconds, while an excessively small time constant will increase the difficulty of background error control; fourth, the existing structure lacks an integrated design for coil positioning, protection, and differential area ratio for the confined space of the vacuum chamber.

[0006] Therefore, a diamagnetic measurement system is needed that combines concentric double-ring geometry, adjustable differential integrator, short time constant design, circumferential field vacuum compensation, poloidal field independent calibration compensation, and energy storage inversion process to adapt to the extraction of weak diamagnetic signals under short-pulse conditions in compact spherical tokamak. Summary of the Invention

[0007] The purpose of this invention is to provide a compact spherical tokamak inverse magnetic flux measurement system and compensation method, which solves the problems of existing technologies being designed for medium and large tokamaks, unable to adapt to the limited space of the vacuum chamber in compact spherical tokamaks, and the strong magnetic flux caused by low toroidal ratio. Overcoming technical limitations such as the circumferential field gradient and the ease with which weak diamagnetic signals under short-pulse conditions can be masked by background errors, this study achieves high-precision extraction and compensation of diamagnetic flux, thereby accurately inverting key macroscopic parameters of plasma and providing reliable support for evaluating the discharge confinement performance of compact spherical tokamak.

[0008] To achieve the above objectives, the present invention provides a compact spherical tokamak inverse magnetic flux measurement system, including a concentric double-loop inverse magnetic coil assembly, a coil positioning support assembly, an adjustable weight differential analog integrator, a circumferential field vacuum compensation unit, a poloidal field dynamic compensation unit, an integral drift correction unit, and a data acquisition and macroscopic parameter inversion unit. The concentric double-ring reverse magnetic coil assembly includes at least one set of inner ring magnetic flux coil and outer ring magnetic flux coil; the inner ring magnetic flux coil and the outer ring magnetic flux coil are arranged at the same circumferential position in the vacuum chamber of the spherical tokamak, and are used to induce output voltage signals respectively during plasma discharge. The coil positioning support assembly is used to attach and fix the outer ring magnetic flux coil to the inner wall of the spherical tokamak vacuum chamber, and to suspend the inner ring magnetic flux coil inside the spherical tokamak vacuum chamber. The input of the adjustable weight differential analog integrator is connected to the concentric double-loop reverse magnetic coil assembly, and its output is connected to the data acquisition and macroscopic parameter inversion unit. The adjustable weight differential analog integrator is used to adjust the weight of the outer loop magnetic flux coil signal, compensate for the residual error caused by the physical difference between the inner loop magnetic flux coil and the outer loop magnetic flux coil, and integrate the induced voltage signal into a reverse magnetic flux signal.

[0009] Preferably, the inner ring magnetic flux coil includes a first inner ring magnetic flux coil and a second inner ring magnetic flux coil suspended in the vacuum chamber of the spherical tokamak, and the outer ring magnetic flux coil includes a first outer ring magnetic flux coil and a second outer ring magnetic flux coil attached to the inner wall of the vacuum chamber of the spherical tokamak. The first inner ring magnetic flux coil and the first outer ring magnetic flux coil, and the second inner ring magnetic flux coil and the second outer ring magnetic flux coil, respectively constitute a differential measurement unit at the same circumferential position; The first inner ring magnetic flux coil, the second inner ring magnetic flux coil, the first outer ring magnetic flux coil, and the second outer ring magnetic flux coil are all made of vacuum-resistant insulated wire with a diameter of 0.7 mm.

[0010] Preferably, the first inner ring magnetic flux coil, the second inner ring magnetic flux coil, the first outer ring magnetic flux coil, and the second outer ring magnetic flux coil are all made of polyimide silver-plated wire with a diameter of 0.7 mm; The winding direction and lead polarity of the first inner loop magnetic flux coil, the second inner loop magnetic flux coil, the first outer loop magnetic flux coil, and the second outer loop magnetic flux coil are set in such a way that the vacuum circumferential field induction terms cancel each other out and the plasma inverse magnetic flux term is retained.

[0011] Preferably, the coil positioning support assembly includes a stainless steel fixing plate, a stud welding support base, a connecting beam, a cable fixing groove, and a positioning cone; Both the first outer ring magnetic flux coil and the second outer ring magnetic flux coil are attached to the inner wall of the spherical tokamak vacuum chamber and fixed by spot welding with stainless steel fixing plates. The first inner ring magnetic flux coil and the second inner ring magnetic flux coil maintain a predetermined distance from the inner wall of the spherical tokamak vacuum chamber and are suspended in the groove of the connecting beam between the stud welded support bases; Both ends of the stud welding support are provided with cable fixing grooves for limiting the cable; the circumferential angle position of the paired inner ring magnetic flux coil and outer ring magnetic flux coil is adjusted by the positioning cone so that they are located at the same circumferential angle with an angle error of no more than 0.05°.

[0012] Preferably, the axial distance between the two cable fixing grooves is 20mm; the center distance between the cables in the cable fixing grooves is 18mm; and the circumferential angle error between the inner and outer ring magnetic flux coils is no greater than 0.05°.

[0013] Preferably, the adjustable weighted differential analog integrator includes a flux measurement signal conditioning circuit and an excitation current drive circuit; The magnetic flux measurement signal conditioning circuit includes a first fixed resistor connected in series with the inner loop magnetic flux coil. and an adjustable resistor connected in series with the outer loop flux coil First fixed resistor Used to receive the inner loop induced voltage And input it to the differential integrator; adjustable resistor A third fixed resistor is connected in series. Used to receive the outer loop induced voltage And input it to the differential integrator; inner loop induced voltage and outer loop induced voltage The measured flux signal is output after integration by the differential integrator. ; The differential integrator includes a first operational amplifier and a first integrating capacitor. First fixed resistor and the third fixed resistor All are connected to the inverting input of the first operational amplifier, and the output of the first operational amplifier is connected to the first integrating capacitor. Connect the inverting input of the first operational amplifier back to the ground; The excitation current drive circuit includes a second fixed resistor. Second operational amplifier and second integrating capacitor Second fixed resistor The second operational amplifier is connected to its inverting input, and its output is connected to its second integrating capacitor. Connect the inverting input of the second operational amplifier back to the circuit, and ground the non-inverting input of the second operational amplifier; the second fixed resistor... Used to receive excitation control signals, via excitation current The drive circuit outputs excitation current. Measure flux signal and excitation current They are connected to the data acquisition and macroscopic parameter inversion unit.

[0014] Preferably, by adjusting the adjustable resistor R 2 By altering the weighting of the outer loop flux coil branch on the vacuum circumferential flux, the differential integral output approaches zero when no plasma is present and only a circumferential field is applied; the integration time constant of the differential integrator... Take 0.1-0.5 ms; differential area ratio of the differential integrator It ranges from 3% to 30%, of which, The effective cross-sectional area of ​​the outer loop flux coil. This represents the difference in area between the inner and outer rings.

[0015] Preferably, the spacing between the inner and outer loop magnetic flux coils is... The integration time constant of the differential integrator is 18mm. The time is 0.2ms; the differential area ratio of the differential integrator. It is 10%.

[0016] Preferably, the toroidal field vacuum compensation unit is used to adjust the adjustable resistor under conditions where there is no plasma and only the toroidal field coil current is applied. Make the output of the differential analog integrator approach zero and establish the vacuum circumferential flux compensation condition; The poloidal field dynamic compensation unit is used to store the coupling coefficients obtained by independently calibrating each poloidal field coil by vacuum energizing it, and to calculate and subtract the stray magnetic flux component of the poloidal field based on the current waveform of each poloidal field coil in plasma discharge data processing. The integral drift correction unit is used to determine the zero-point drift trend of the integrator by utilizing the plasma-free region before and after discharge, and to measure the flux signal. Perform baseline correction.

[0017] The present invention also provides a compensation method for a compact spherical tokamak inverse magnetic flux measurement system, comprising the following steps: S1. Under the condition that only longitudinal magnetic flux exists, i.e., without plasma and poloidal magnetic field, adjust the adjustable resistor. This makes the output of the differential integrator zero, and measures the flux signal. =0, resulting in: ; in, The magnetic flux induced in the outer ring under the vacuum loop field. The magnetic flux induced in the inner ring under the vacuum loop field; S2. Under plasma discharge conditions, the reverse magnetic flux for: ; S3. Perform stray magnetic field compensation on the measurement results. The compensation amount includes: Subtracting the toroidal field flux: When using a single toroidal field, the adjustable resistor is gradually adjusted. This causes the integrator output signal to subtract the circumferential field flux; Eddy current subtraction: This refers to the subtraction of eddy currents primarily caused by variations in the circumferential field current. or the time gradient of the circumferential field current Provide compensation; Subtracting stray magnetic flux generated by the current in the poloidal field coils: compensating for the stray fields of the 10 poloidal field coils; S4. Based on the stray magnetic field compensation requirements of S3, the compensated diamagnetic flux. Determined by the following formula: ; in, This represents the compensation coefficient for the circumferential field. For the compensation coefficient of the poloidal field, It is the poloidal field current.

[0018] Therefore, the present invention employs the above-mentioned compact spherical tokamak inverse magnetic flux measurement system and compensation method, and the beneficial effects are as follows: 1) Improved background suppression under compact spatial conditions: This invention utilizes an inner and outer concentric ring differential structure and Adjustable weight matching, under vacuum circumferential field conditions, brings the integral output close to zero, significantly reducing the masking effect of vacuum circumferential magnetic flux on weak diamagnetic signals. The residual error flux after vacuum compensation in the circumferential field can be controlled within 1.6 × 10⁻⁶. -5 Within Wb.

[0019] 2) Balancing short-pulse transient response and signal amplitude: In this invention The small time constant of 0.2ms is designed to adapt to the short pulse operation conditions of NCST on the order of hundreds of milliseconds, which can improve the response capability to rapid changes in energy storage; under typical reverse magnetic flux - Within the Wb range, the integrator output is approximately 30-300mV, facilitating stable data acquisition.

[0020] 3) Reduced dependence on the accuracy of coil absolute geometric area measurement: This invention determines the accuracy through circumferential field vacuum calibration. The effective conversion factor does not necessarily depend entirely on the difference in effective area between the inner and outer rings after installation. Direct measurement reduces the impact of coil deformation, assembly deviation, and vacuum chamber structural errors on the inversion results.

[0021] 4) Suppressing dynamic coupling error in the poloidal field: This invention establishes the coupling relationship between the poloidal field current and stray magnetic flux by independently calibrating the poloidal field sources, such as the ohmic field coil and the vertical field coil, and subtracts the corresponding dynamic component from the plasma discharge data. In a preferred embodiment, the compensated overall relative residual error is less than 1.8% of the typical inverse magnetic flux change.

[0022] 5) Compact structure and easy to repeat installation: The stud welding support, cable fixing groove, positioning cone and connecting beam structure of the present invention can position and protect the suspended inner ring in the confined space of the vacuum chamber, so that the differential pairing coils keep the same circumferential position, which is beneficial to improving the repeatability between multiple installations and multiple discharges.

[0023] 6) Supports macroscopic parameter estimation and joint diagnostic analysis; the system of this invention can output macroscopic parameters such as diamagnetic flux, poloidal specific pressure, energy storage, and energy confinement time, and can be integrated with... , , Synchronous analysis of signals provides an experimental data foundation for identifying the energy storage evolution during the discharge process of a short-pulse compact tokamak. The aforementioned macroscopic parameters are application outputs based on the compensated inverse magnetic flux and can serve as a data source for device operation analysis and subsequent control research.

[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the concentric double-ring differential integration measurement principle of an embodiment of the compact spherical tokamak inverse magnetic flux measurement system of the present invention; Figure 2 This is a schematic diagram of the relative arrangement of the concentric double-ring inverse magnetic coil assembly in the NCST device according to an embodiment of the compact spherical tokamak inverse magnetic flux measurement system of the present invention; Figure 3 This is a schematic diagram of the overall structure of the spherical tokamak vacuum chamber according to an embodiment of the compact spherical tokamak inverse magnetic flux measurement system of the present invention; Figure 4 This is a cross-sectional view of an embodiment of a compact spherical tokamak inverse magnetic flux measurement system according to the present invention; Figure 5 This is a schematic diagram of the concentric double-ring reverse magnetic coil assembly according to an embodiment of the compact spherical tokamak reverse magnetic flux measurement system of the present invention; Figure 6 This is another cross-sectional view of an embodiment of the compact spherical tokamak inverse magnetic flux measurement system of the present invention; Figure 7 This is an embodiment of a compact spherical tokamak inverse magnetic flux measurement system according to the present invention. Figure 6 Enlarged view of point A in the middle; Figure 8 This is a schematic diagram of the stud-welded support structure of the concentric double-ring reverse magnetic coil assembly in an embodiment of the compact spherical tokamak reverse magnetic flux measurement system of the present invention. Figure 9 This is a comparison diagram of the output signals before and after circumferential field vacuum background compensation in an embodiment of the compact spherical tokamak inverse magnetic flux measurement system of the present invention. In this diagram, (a) represents the discharge of #240517010, with a resistance ratio of... / =9.92%, (b) is the discharge of #240517012, resistance ratio / =10.00%; (c) discharge of #240517013, resistance ratio / =9.96%; (d) is the discharge of #240517016, resistance ratio / =9.96%; Figure 10 This is a comparison diagram of poloidal field dynamic compensation and plasma dimagnetic response of an embodiment of a compact spherical tokamak diamagnetic flux measurement system of the present invention, wherein (a) is plasma current, (b) is circumferential magnetic field, (c) is diamagnetic flux, (d) is poloidal specific pressure, and (e) is energy storage.

[0026] Figure Labels 101. Concentric Double-Ring Reverse Magnetic Coil Assembly; 1. Inner Ring Magnetic Flux Coil; 01a. First Inner Ring Magnetic Flux Coil; 02a. Second Inner Ring Magnetic Flux Coil; 2. Outer Ring Magnetic Flux Coil; 01b. First Outer Ring Magnetic Flux Coil; 02b. Second Outer Ring Magnetic Flux Coil; 3. Stud Welding Support; 4. Connecting Beam; 5. Cable Fixing Groove; 6. Positioning Conical Hole; 7. Connecting Beam Fixing Hole; 8. Stud Adjustment Hole; 9. Rogowski Coil; 10. Magnetic Flux Ring; 11. Magnetic Probe; 12. Spherical Tokamak Vacuum Chamber. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0029] like Figures 1-10 As shown, this invention discloses a compact spherical tokamak inverse magnetic flux measurement system, comprising a concentric double-loop inverse magnetic coil assembly 101, a coil positioning support assembly, an adjustable weighted differential simulation integrator, a circumferential field vacuum compensation unit, a poloidal field dynamic compensation unit, an integral drift correction unit, and a data acquisition and macroscopic parameter inversion unit. This system is used in the confined space of a spherical tokamak vacuum chamber and in strong 1 / R Weak diamagnetic flux is extracted under circumferential field gradient conditions, and parameters such as poloidal specific pressure and diamagnetic energy storage are further output.

[0030] like Figure 4 , Figure 5As shown, the concentric double-ring inverse magnetic coil assembly 101 of the present invention includes at least one set of inner ring magnetic flux coil 1 and outer ring magnetic flux coil 2; the inner ring magnetic flux coil 1 and the outer ring magnetic flux coil 2 are disposed at the same circumferential position within the spherical tokamak vacuum chamber 12, and are used to respectively induce and output voltage signals during plasma discharge. A coil positioning support assembly is used to attach and fix the outer ring magnetic flux coil 2 to the inner wall of the spherical tokamak vacuum chamber 12, and to suspend the inner ring magnetic flux coil 1 inside the spherical tokamak vacuum chamber 12. The input terminal of an adjustable weight differential analog integrator is connected to the concentric double-ring inverse magnetic coil assembly 101, and its output terminal is connected to a data acquisition and macroscopic parameter inversion unit. The adjustable weight differential analog integrator is used to adjust the weight of the outer ring magnetic flux coil signal, compensate for residual errors caused by physical differences between the inner and outer ring magnetic flux coils, and integrate the induced voltage signal into an inverse magnetic flux signal.

[0031] like Figure 6 , Figure 7 As shown, in this embodiment, the concentric double-ring reverse magnetic coil assembly 101 is provided with two sets of inner ring magnetic flux coils 1 and outer ring magnetic flux coils 2. The inner ring magnetic flux coil 1 includes a first inner ring magnetic flux coil 01a and a second inner ring magnetic flux coil 02a that are suspended in the air. The outer ring magnetic flux coil 2 includes a first outer ring magnetic flux coil 01b and a second outer ring magnetic flux coil 02b that are attached to the inner wall of the spherical tokamak vacuum chamber 12.

[0032] The first inner ring magnetic flux coil 01a and the first outer ring magnetic flux coil 01b, and the second inner ring magnetic flux coil 02a and the second outer ring magnetic flux coil 02b, respectively constitute a differential measurement unit at the same circumferential position. The first inner ring magnetic flux coil 01a, the second inner ring magnetic flux coil 02a, the first outer ring magnetic flux coil 01b, and the second outer ring magnetic flux coil 02b are all made of vacuum-resistant insulated wire with a diameter of 0.7mm.

[0033] In specific implementation, the first inner ring magnetic flux coil 01a, the second inner ring magnetic flux coil 02a, the first outer ring magnetic flux coil 01b, and the second outer ring magnetic flux coil 02b all use polyimide silver-plated wire with a diameter of 0.7mm. The coil winding direction and lead-out polarity of the first inner ring magnetic flux coil 01a, the second inner ring magnetic flux coil 02a, the first outer ring magnetic flux coil 01b, and the second outer ring magnetic flux coil 02b are set in a way that cancels out the vacuum circumferential field induction terms and retains the plasma reverse magnetic flux term.

[0034] like Figure 5 As shown, the coil positioning support assembly of the present invention includes a stainless steel fixing plate (not shown in the figure), a stud welding support base 3, a connecting beam 4, a cable fixing groove 5, and a positioning cone.

[0035] The first outer ring magnetic flux coil 01b and the second outer ring magnetic flux coil 02b are both attached to the inner wall of the spherical tokamak vacuum chamber 12 and fixed by spot welding with stainless steel fixing plates.

[0036] The first inner ring magnetic flux coil 01a and the second inner ring magnetic flux coil 02a maintain a predetermined distance from the inner wall of the spherical tokamak vacuum chamber 12 and are suspended in the connecting beam groove between the stud welded support base 3.

[0037] The stud welding support 3 has cable fixing grooves 5 at both its upper and lower ends for limiting the cable. The circumferential angle position of the mating ring magnetic flux coil and the outer ring magnetic flux coil is adjusted by the positioning cone so that they are located at the same circumferential angle with an angle error of no more than 0.05°. In this embodiment, the axial distance between the two cable fixing grooves 5 is set to 20mm; and the center distance between the cables in the cable fixing grooves 5 is 18mm; the circumferential angle error between the inner ring magnetic flux coil and the outer ring magnetic flux coil is no more than 0.05°.

[0038] The adjustable weighted differential analog integrator of the present invention includes a flux measurement signal conditioning circuit and an excitation current driving circuit; the flux measurement signal conditioning circuit includes a first fixed resistor connected in series with the inner loop flux coil 1. and the adjustable resistor connected in series with the outer loop flux coil 2 .

[0039] First fixed resistor Used to receive the inner loop induced voltage And input it to the differential integrator; adjustable resistor A third fixed resistor is connected in series. Used to receive the outer loop induced voltage And input it to the differential integrator; inner loop induced voltage and outer loop induced voltage The measured flux signal is output after integration by the differential integrator. In this embodiment, the first fixed resistor and the third fixed resistor The resistance values ​​are equal.

[0040] The differential integrator includes a first operational amplifier and a first integrating capacitor. First fixed resistor and the third fixed resistor All are connected to the inverting input of the first operational amplifier, and the output of the first operational amplifier is connected to the first integrating capacitor. Connect the inverting input of the first operational amplifier back to the ground, and ground the non-inverting input of the first operational amplifier.

[0041] The excitation current drive circuit includes a second fixed resistor. Second operational amplifier and second integrating capacitor Second fixed resistor The second operational amplifier is connected to its inverting input, and its output is connected to its second integrating capacitor. Connect the inverting input of the second operational amplifier back to the circuit, and ground the non-inverting input of the second operational amplifier; the second fixed resistor... Used to receive excitation control signals, via excitation current The drive circuit outputs excitation current. Measure flux signal and excitation current They are jointly connected to the data acquisition and macroscopic parameter inversion unit. In this embodiment, the first integrating capacitor... Second Integrating Capacitor The capacitance values ​​are equal.

[0042] In actual use, the adjustable resistor is adjusted. R 2 By altering the weighting of the outer loop flux coil branch on the vacuum circumferential flux, the differential integral output approaches zero when no plasma is present and only a circumferential field is applied. The integration time constant of the differential integrator is then set. Take 0.1-0.5 ms; differential area ratio of the differential integrator It ranges from 3% to 30%, of which, The effective cross-sectional area of ​​the outer loop flux coil. This represents the difference in area between the inner and outer rings.

[0043] In specific implementation, the spacing between the inner ring magnetic flux coil 1 and the outer ring magnetic flux coil 2... The integration time constant of the differential integrator is 18mm. The time is 0.2ms; the differential area ratio of the differential integrator. The preferred parameters for this embodiment are as follows: 10%. Table 1 Preferred Parameters of the Invention

[0044] Furthermore, the toroidal field vacuum compensation unit of the present invention is used to adjust the adjustable resistor under conditions of no plasma and only the application of toroidal field coil current. The output of the differential analog integrator is brought close to zero to establish the vacuum circumferential flux compensation condition.

[0045] The poloidal field dynamic compensation unit is used to store the coupling coefficients obtained by independently calibrating each poloidal field coil through vacuum energization, and to calculate and subtract the stray magnetic flux component of the poloidal field based on the current waveform of each poloidal field coil in plasma discharge data processing.

[0046] The integral drift correction unit is used to determine the zero-point drift trend of the integrator by utilizing the plasma-free region before and after discharge, and to measure the flux signal. Perform baseline correction.

[0047] like Figure 1 As shown, the inner loop magnetic flux coil 1 and the outer loop magnetic flux coil 2, located near the cross-section of the spherical tokamak vacuum chamber 12, respectively output the inner loop induced voltage. and outer loop induced voltage ; Outer loop induced voltage via the third fixed resistor With adjustable resistor The series branch input differential integrator, inner loop induced voltage Through the first fixed resistor The branch input differential integrator receives both signals via the first integrating capacitor. The output flux measurement signal is obtained by integrating with the operational amplifier. . Figure 1 The dark gray area on the left side represents the plasma during tokamak discharge. This plasma can be controlled by adjusting the adjustable resistor. This allows the vacuum background terms to cancel each other out at the output when there is no plasma and only a circumferential field is applied, thus establishing a circumferential field vacuum compensation condition; during plasma discharge, the compensated output signal is used to invert the inverse magnetic flux.

[0048] like Figure 2 , Figure 4 and Figure 6 As shown, a concentric double-ring reverse magnetic coil assembly 101 is arranged near the cross section to be measured, including at least one set of inner ring magnetic flux coil 1 and outer ring magnetic flux coil 2. The inner ring magnetic flux coil 1 and outer ring magnetic flux coil 2 are paired at the same circumferential position to form a differential measurement unit. Figure 1 Other magnetic diagnostic components, such as Rogowski coil 9, flux loop 10, and magnetic probe 11, are auxiliary diagnostic components in the device environment, used to illustrate the arrangement of the present invention in a compact vacuum chamber, and do not constitute a necessary limitation of the present invention.

[0049] like Figures 3-7 As shown, the outer ring magnetic flux coil 2 is attached to the wall of the spherical tokamak vacuum chamber 12 and fixed by a fixing plate; the inner ring magnetic flux coil 1 is suspended on the positioning structure formed by the stud welded support 3 and the connecting beam 4, maintaining a predetermined distance from the outer ring magnetic flux coil 2.

[0050] like Figure 8As shown, the cable fixing groove 5 on the stud welding support 3 is used to define the axial position of the inner ring magnetic flux coil 1 and the center distance of the cables. The positioning cone is used to adjust the circumferential angle alignment between the inner ring magnetic flux coil 1 and the outer ring magnetic flux coil 2. The stud welding support 3 is provided with a positioning cone hole 6, a connecting beam fixing hole 7, and a stud adjustment hole 8 for fixing and installing various components. This installation structure can ensure the differential area ratio and circumferential alignment accuracy under the limited space of the vacuum chamber, and reduce the background magnetic field coupling error caused by installation eccentricity.

[0051] Figure 9 It includes four vacuum discharge integral output voltages with only a circumferential field applied, each corresponding to a different... / Settings. Among them, and The original integral signal is represented by the inner and outer concentric loops, and Diam is represented by the signal after passing through a differential integrator and an adjustable resistor. The compensated output voltage after weight adjustment. Figure 9 (a) in the figure represents the discharge of #240517010, with a resistance ratio of / =9.92%; Figure 9 (b) in the diagram represents the discharge of #240517012, with a resistance ratio of / =10.00%; Figure 9 (c) in the figure represents the discharge of #240517013, with a resistance ratio of / =9.96%; Figure 9 (d) in the figure represents the discharge of #240517016, with a resistance ratio of / =9.96%, and each sub-attachment is a partial enlarged view of the compensated output voltage under the corresponding operating condition.

[0052] from Figure 9 The results of vacuum circumferential field flux compensation show that by adjusting the adjustable resistor... This allows the originally large vacuum circumferential field induced signals to cancel each other out at the output end, resulting in a compensated output signal close to zero. Furthermore, this invention allows the adjustable resistor to be determined through vacuum circumferential field calibration. The compensation position is determined, and the influence of the circumferential field common-mode background on the measurement of weak diamagnetic signals is effectively reduced.

[0053] like Figure 10 As shown, vacuum discharge data is used to determine the coupling relationship between poloidal field sources such as ohmic field coils and vertical field coils and the concentric double-loop differential output; plasma discharge data is used to demonstrate the inverse magnetic flux response after subtracting the poloidal field stray component. Figure 10Figures (a)-(e) sequentially show the plasma current, circumferential magnetic field, compensated contramagnetic flux, poloidal specific pressure estimated from the contramagnetic flux, and energy storage time evolution. This figure illustrates that after completing circumferential field vacuum compensation, further subtracting the dynamic coupling term based on the poloidal field coil current waveform can reduce the pseudo-contramagnetic signal introduced by poloidal field changes and make the plasma energy storage evolution signal distinguishable.

[0054] The process of inventing a method for measuring and compensating inverse magnetic flux is as follows: First, the installation and geometric parameter setting of the inner loop magnetic flux coil 1 and the outer loop magnetic flux coil 2 are completed; second, the circumferential field vacuum calibration is performed under plasma-free conditions, and the adjustable resistor is adjusted. A conversion factor is established; then, each poloidal field coil is independently energized and calibrated to obtain the poloidal field coupling coefficient; during the plasma discharge process, the differential integral output and the current waveform of each coil are collected, and the poloidal field stray component subtraction, integral drift correction and inverse magnetic flux inversion are performed in sequence to finally output parameters such as inverse magnetic flux, poloidal specific pressure, energy storage and energy confinement time.

[0055] The present invention provides a compensation method for a compact spherical tokamak inverse magnetic flux measurement system, comprising the following steps: S1. Under the condition that only longitudinal magnetic flux exists, i.e., without plasma and poloidal magnetic field, adjust the adjustable resistor. This makes the output of the differential integrator zero, and measures the flux signal. =0, we can get: ; in, The magnetic flux induced in the outer ring under the vacuum loop field. The inner ring induced magnetic flux under the vacuum toroidal field.

[0056] This step yields an adjustable resistor. With the second fixed resistor The ratio of the resistance values.

[0057] S2. Under plasma discharge conditions, the reverse magnetic flux for: .

[0058] As shown in the above formula, the reverse magnetic flux It can be made by the first fixed resistor Adjustable resistor and the first integrating capacitor get.

[0059] S3. Perform stray magnetic field compensation on the measurement results. The compensation amount includes: ①Subtract the circumferential magnetic flux: When using a single-pole toroidal field, the integrator output is not exactly zero: it requires gradual adjustment of the adjustable resistor. This ensures that the integrator output signal deducts the circumferential field flux as much as possible.

[0060] ②Subtract eddy currents: To address the eddy currents primarily caused by variations in the circumferential field current, it is necessary to analyze the circumferential field current. or the time gradient of the circumferential field current Compensation will be provided.

[0061] ③Subtract the stray magnetic flux generated by the current in the poloidal field coil: Although the poloidal field generated by the poloidal coils is parallel to that of the concentric coils, the concentric coils can still measure a certain amount of poloidal magnetic flux due to installation errors. Stray field compensation is required for the 10 poloidal coils.

[0062] S4. Based on the stray magnetic field compensation requirements of S3, the compensated diamagnetic flux. Determined by the following formula: ; in, This represents the compensation coefficient for the circumferential field. For the compensation coefficient of the poloidal field, The poloidal current; the compensation coefficient of the poloidal field. and the compensation coefficient of the circumferential field It is obtained by separately distributing the currents in each field.

[0063] Therefore, this invention employs the aforementioned compact spherical tokamak inverse magnetic flux measurement system and compensation method. By compensating for residual errors through a concentric double-ring differential structure and an adjustable integrator, combined with multi-unit collaborative compensation to suppress interference, and relying on positioning components to ensure installation accuracy, it achieves high-precision extraction of weak inverse magnetic signals under short-pulse conditions. It can accurately invert key plasma parameters, is compatible with compact spherical tokamaks, and fills the application gap of existing inverse magnetic measurement technology in the field of compact spherical tokamaks. It has significant technical advantages such as compact structure, high measurement accuracy, and strong adaptability.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A compact spherical tokamak inverse magnetic flux measurement system, characterized in that: It includes a concentric double-ring reverse magnetic coil assembly, a coil positioning support assembly, an adjustable weight differential simulation integrator, a circumferential field vacuum compensation unit, a poloidal field dynamic compensation unit, an integral drift correction unit, and a data acquisition and macroscopic parameter inversion unit; The concentric double-ring reverse magnetic coil assembly includes at least one set of inner ring magnetic flux coil and outer ring magnetic flux coil; the inner ring magnetic flux coil and the outer ring magnetic flux coil are arranged at the same circumferential position in the vacuum chamber of the spherical tokamak, and are used to induce output voltage signals respectively during plasma discharge. The coil positioning support assembly is used to attach and fix the outer ring magnetic flux coil to the inner wall of the spherical tokamak vacuum chamber, and to suspend the inner ring magnetic flux coil inside the spherical tokamak vacuum chamber. The input of the adjustable weight differential analog integrator is connected to the concentric double-loop reverse magnetic coil assembly, and its output is connected to the data acquisition and macroscopic parameter inversion unit. The adjustable weight differential analog integrator is used to adjust the weight of the outer loop magnetic flux coil signal, compensate for the residual error caused by the physical difference between the inner loop magnetic flux coil and the outer loop magnetic flux coil, and integrate the induced voltage signal into a reverse magnetic flux signal.

2. The compact spherical tokamak inverse magnetic flux measurement system according to claim 1, characterized in that: The inner loop magnetic flux coil includes a first inner loop magnetic flux coil and a second inner loop magnetic flux coil suspended in the vacuum chamber of the spherical tokamak, and the outer loop magnetic flux coil includes a first outer loop magnetic flux coil and a second outer loop magnetic flux coil attached to the inner wall of the vacuum chamber of the spherical tokamak. The first inner ring magnetic flux coil and the first outer ring magnetic flux coil, and the second inner ring magnetic flux coil and the second outer ring magnetic flux coil, respectively constitute a differential measurement unit at the same circumferential position; The first inner ring magnetic flux coil, the second inner ring magnetic flux coil, the first outer ring magnetic flux coil, and the second outer ring magnetic flux coil are all made of vacuum-resistant insulated wire with a diameter of 0.7 mm.

3. The compact spherical tokamak inverse magnetic flux measurement system according to claim 2, characterized in that: The first inner ring magnetic flux coil, the second inner ring magnetic flux coil, the first outer ring magnetic flux coil, and the second outer ring magnetic flux coil all use polyimide silver-plated wire with a diameter of 0.7 mm; The winding direction and lead polarity of the first inner loop magnetic flux coil, the second inner loop magnetic flux coil, the first outer loop magnetic flux coil, and the second outer loop magnetic flux coil are set in such a way that the vacuum circumferential field induction terms cancel each other out and the plasma inverse magnetic flux term is retained.

4. The compact spherical tokamak inverse magnetic flux measurement system according to claim 3, characterized in that, The coil positioning support assembly includes a stainless steel fixing plate, a stud welding support base, a connecting beam, a cable fixing groove, and a positioning cone; Both the first outer ring magnetic flux coil and the second outer ring magnetic flux coil are attached to the inner wall of the spherical tokamak vacuum chamber and fixed by spot welding with stainless steel fixing plates. The first inner ring magnetic flux coil and the second inner ring magnetic flux coil maintain a predetermined distance from the inner wall of the spherical tokamak vacuum chamber and are suspended in the groove of the connecting beam between the stud welded support bases; Both ends of the stud welding support are provided with cable fixing grooves for limiting the cable; the circumferential angle position of the paired inner ring magnetic flux coil and outer ring magnetic flux coil is adjusted by the positioning cone so that they are located at the same circumferential angle with an angle error of no more than 0.05°.

5. A compact spherical tokamak inverse magnetic flux measurement system according to claim 4, characterized in that, The axial distance between the two cable fixing grooves is 20mm; the center distance between the cables in the cable fixing grooves is 18mm; the circumferential angle error between the inner and outer magnetic flux coils is no greater than 0.05°.

6. A compact spherical tokamak inverse magnetic flux measurement system according to claim 5, characterized in that, The adjustable weighted differential analog integrator includes a flux measurement signal conditioning circuit and an excitation current drive circuit; The magnetic flux measurement signal conditioning circuit includes a first fixed resistor connected in series with the inner loop magnetic flux coil. and an adjustable resistor connected in series with the outer loop flux coil First fixed resistor Used to receive the inner loop induced voltage And input it into the differential integrator; Adjustable resistor A third fixed resistor is connected in series. Used to receive the outer loop induced voltage And input it to the differential integrator; inner loop induced voltage and outer loop induced voltage The measured flux signal is output after integration by the differential integrator. ; The differential integrator includes a first operational amplifier and a first integrating capacitor. First fixed resistor and the third fixed resistor All are connected to the inverting input of the first operational amplifier, and the output of the first operational amplifier is connected to the first integrating capacitor. Connect the inverting input of the first operational amplifier back to the ground; The excitation current drive circuit includes a second fixed resistor. Second operational amplifier and second integrating capacitor Second fixed resistor The second operational amplifier is connected to its inverting input, and its output is connected to its second integrating capacitor. Connect the inverting input of the second operational amplifier back to the circuit, and ground the non-inverting input of the second operational amplifier; the second fixed resistor... Used to receive excitation control signals, via excitation current The drive circuit outputs excitation current. Measure flux signal and excitation current They are connected to the data acquisition and macroscopic parameter inversion unit.

7. A compact spherical tokamak inverse magnetic flux measurement system according to claim 6, characterized in that, By adjusting the adjustable resistor R 2 By altering the weighting of the outer loop flux coil branch on the vacuum circumferential flux, the differential integral output approaches zero when no plasma is present and only a circumferential field is applied; the integration time constant of the differential integrator... Take 0.1-0.5 ms; differential area ratio of the differential integrator It ranges from 3% to 30%, of which, The effective cross-sectional area of ​​the outer loop flux coil. This represents the difference in area between the inner and outer rings.

8. A compact spherical tokamak inverse magnetic flux measurement system according to claim 7, characterized in that, The spacing between the inner and outer loop flux coils The integration time constant of the differential integrator is 18mm. The time is 0.2ms; the differential area ratio of the differential integrator. It is 10%.

9. A compact spherical tokamak inverse magnetic flux measurement system according to claim 8, characterized in that, A toroidal field vacuum compensation unit is used to compensate for vacuum pressure in the absence of plasma and by adjusting an adjustable resistor when only toroidal field coil current is applied. Make the output of the differential analog integrator approach zero and establish the vacuum circumferential flux compensation condition; The poloidal field dynamic compensation unit is used to store the coupling coefficients obtained by independently calibrating each poloidal field coil by vacuum energizing it, and to calculate and subtract the stray magnetic flux component of the poloidal field based on the current waveform of each poloidal field coil in plasma discharge data processing. The integral drift correction unit is used to determine the zero-point drift trend of the integrator by utilizing the plasma-free region before and after discharge, and to measure the flux signal. Perform baseline correction.

10. A compensation method for a compact spherical tokamak inverse magnetic flux measurement system, employing the system described in any one of claims 1-9, characterized in that, Includes the following steps: S1. Under the condition that only longitudinal magnetic flux exists, i.e., without plasma and poloidal magnetic field, adjust the adjustable resistor. This makes the output of the differential integrator zero, and measures the flux signal. =0, resulting in: ； in, The magnetic flux induced in the outer ring under the vacuum loop field. The magnetic flux induced in the inner ring under the vacuum loop field; S2. Under plasma discharge conditions, the reverse magnetic flux for: ； S3. Perform stray magnetic field compensation on the measurement results. The compensation amount includes: Subtracting the toroidal field flux: When using a single toroidal field, the adjustable resistor is gradually adjusted. This causes the integrator output signal to subtract the circumferential field flux; Eddy current subtraction: This refers to the subtraction of eddy currents primarily caused by variations in the circumferential field current. or the time gradient of the circumferential field current Provide compensation; Subtracting stray magnetic flux generated by the current in the poloidal field coils: compensating for the stray fields of the 10 poloidal field coils; S4. Based on the stray magnetic field compensation requirements of S3, the compensated diamagnetic flux. Determined by the following formula: ； in, This represents the compensation coefficient for the circumferential field. For the compensation coefficient of the poloidal field, It is the poloidal field current.

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