Plasma current measurements by Faraday rotation in a single-mode fiber

Abstract

We report measurements of the toroidal plasma current in the high-beta tokamak SPICA II using a magnetooptic current sensor. Both the sine and cosine components of the angle of rotation are recorded during the current pulse. In this way, the overall accuracy is increased and a computer algorithm can be employed to calculate the value of the current. The effect of linear birefringence is taken into account. The system has a resolution of 1 kA, and a frequency range of DC to 1 MHz. The measured values of the plasma current (up to 350 kA) are in good agreement with the results of a Rogowski coil.