Engineering Design of Plasma Current Measurement in EXL-50U Spherical Torus: Integrating Rogowski Coil and Water-Cooled Optical Fiber Sensors

Accurate plasma current measurement is essential for the control and analysis of plasma behavior in tokamak experiments. In the EXL-50U spherical torus, a synergistic measurement system combining Rogowski coils, strategically positioned 180° apart, with optical fiber current sensors has been implemented. To meet the rigorous demands of high-temperature of plasma experiments, a dedicated water-cooling system was engineered to protect and efficiently cool the optical fibers within the vacuum vessel. Calibration procedures employing a FLUKE current source were done after the installation and the two kinds of sensors show good consistency in measuring the plasma current. The research overcame significant design and installation obstacles, such as reducing eddy current interference from toroidal structures and preventing damage to the optical fibers during installation, by employing innovative engineering strategies. These advancements contribute significantly to the field of fusion energy, enhancing the accuracy and reliability of plasma diagnostics.