Optics-based measurements of temporal evolution of currents through a load of X-pinch system using Tb-doped optic fiber*

An X-pinch system is capable of generating high energy density plasmas with pulsed and large currents through a load which typically consists of a pair of crossed thin wires. Temporal evolution of the currents through the load can be used to identify various stages of the X-pinch system such as ablation of the wires, formation of plasmas, or emission of X-rays from the hot-spot. To measure such currents on the X-pinch system, we construct an optics-based diagnostic system capable of measuring up to a few MA scale of currents with fast response time. The sensing material is an optic fiber wound around the load to detect the Faraday rotation induced by the currents through the load. More specifically, Tb-doped optic fiber is used since its sensitivity to the Faraday rotation is approximately an order of magnitude greater than general optic fibers. As a result, the required fiber length becomes shorter, thus, providing us better temporal resolution. We present configuration of our optics-based current diagnostic system and the measurement results of the temporal evolution of the currents through the load of the X-pinch system.