Measurements of the current evolution on a load of X-pinch system using the Faraday rotation with spun fibers

A measurement system based on optic fibers is developed to measure currents on a load of the SNU X-pinch device [1]. As a high and fast current pulse is driven, electric circuit-based sensors are likely to be damaged by high electric fields. In addition, distortion of the measured signals is expected due to broadband electromagnetic waves induced by the pulsed high voltage sources. Hence, we construct the current measurement system using optic fibers such that the sensor part around the load is made with electrically insulated materials and the required electronic devices, e.g., a laser source, photo-detectors and oscilloscopes, can be shielded in a Faraday cage. The optic fiber is wound around the load to detect the Faraday rotation of the polarization state induced by the load current. We present configuration of the current measurement system using the spun fibers, which is better for maintaining an arbitrary polarization state compared to other types of optic fibers. We, then, compare temporal evolutions of the measured currents for the cases of a short circuit, a single wire and an X-wire load.