شبيه سازي ميدان هاي مغناطيسي توكامك الوند

Magnetic field simulation in tokamaks is crucial for optimizing plasma confinement. This study aims to analyze the magnetic fields generated by the coils of the Alvan‎d Tokamak an‎d validate the results through calibration of coils an‎d magnetic probes. Three-dimensional simulations using COMSOL were performed, including helical coils, the central solenoid, vertical coils, an‎d correction coils. The helical field at the center of the vessel was calculated as 0.94 T theoretically an‎d 0.95  T in simulation. Helical coils were analyzed in both ideal an‎d realistic configurations, yielding a wave parameter of 4  % for the realistic case an‎d 6 % for the ideal case at a radius of 58 cm.the central solenoid plays a key role in producing a uniform magnetic field in the midsection of the vessel, significantly affecting field strength an‎d distribution. Simulation results show that the field generated by this coil peaks at the center an‎d gradually decreases toward the edges, consistent with theoretical predictions. Vertical coils help stabilize the field along the Z-axis, reducing local variations an‎d enhancing vertical uniformity. The combined effect of the central an‎d vertical coils allows better magnetic field control throughout the vessel an‎d improves plasma stability. In the calibration section, the helical, central, an‎d vertical coil probes were calibrated using a Rogowski wire coil; the magnetic field per unit current for toroidal coils was calculated as 0.63×〖10〗^(-5) an‎d 0.62×〖10〗^(-5)in simulation an‎d experiment, respectively, with a relative error of 0.1 %. The calibration coefficients for the central solenoid an‎d vertical coils were approximately 1200  V/A an‎d 4.95  V/A, respectively. A reference laboratory setup with a stan‎dard coil was provided, an‎d probes were placed at its center. Calibration of poloidal an‎d radial probes using a Pearson Rogowski coil resulted in final coefficients of 243 G/V an‎d 100  G/V, respectively. Comparison with a cylindrical coil numerical model based on Ampère’s law showed that the central field matched experimental data with less than 0.3 % deviation. These results confirm the accuracy of the simulations, the reliability of the calibration process, an‎d the importance of precise coil design in the Alvan‎d Tokamak.

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