Magnetic Field Measurements in Wire-Array Z-Pinches Using Magnetoactive Materials

Abstract

Summary form only given. It is generally believed that understanding the magnetic field topology in wire-array Z-pinches as a function of time is of great importance to understanding these high-energy density plasmas. As part of our continuing effort to develop new methods to measure the magnetic field as a function of position and time in wire-array Z-pinches, we are carrying out experiments using Faraday rotation of a single mode laser beam into a magneto-active glass that is placed adjacent to, or within, the wire array in experiments on the COBRA pulsed power generator. We present experimental and theoretical results of the magnetic field profile outside of a wire array, and preliminary results within the array, in the particular geometry used for the COBRA experiments. We also present our progress on measurements involving a very small "thin film waveguide" placed near or in a wire array, with the waveguide coupled to an optical fiber system to record the Faraday rotation of the laser as it passes through the thin film waveguide. While these sensing devices may not survive for long in a dense Z-pinch, they may provide useful information on the magnetic field at the position of the sensor (glass or waveguide) for a significant fraction of the current pulse. We also compare our results with magnetic probe measurements at the same place with the same test pulses.