Development of the current driver and diagnostics for magnetic field measurements of Formosa Integrated Research Spherical Tokamak (FIRST), the first Tokamak in Taiwan

The first Tokamak in Taiwan, Formosa Integrated Research Spherical Tokamak (FIRST), is under construction. We are aiming to achieve the first plasma in 2026. In this work, we are focusing on building the current drivers of all coils and diagnostics for magnetic-field measurements. The current drivers consist of supercapacitors, IGBT modules, and pulse-width modulation to provide the required current profiles. A toroidal field of ~0.1 T on the geometrical axis will be generated by 16 toroidal-field coils driven by a current of ~14 kA lasting up to 100 ms. An equilibrium state with a major and a minor radius of 45 cm and 32 cm, respectively, will potentially be achieved by 12 poloidal-field coils. A central solenoid will initiate plasma breakdown and provide ohmic heating. On the other hand, simple flux loops and 3-axis B-dot probes will be installed inside the chamber to measure the magnetic flux and fields for equilibrium reconstructions. The 3-axis B-dot probe is being built and calibrated using a 3-axis Helmholtz coil. The design, development, and testing results of the current driver systems and the three-axis B-dot probe diagnostics will be presented.