Developing an interferometer for electron density measurements of low density plasmas on the Z Machine

Large current densities on transmission lines that deliver power to the target on the Z Machine are hypothesized to generate low density plasmas, potentially causing significant current loss. Electron density is a key parameter in quantitatively characterizing these low density power flow plasmas. The implementation of a shearing interferometer is discussed in this work to measure the line integrated electron density. This interferometer will be additionally used to support a Faraday Rotation imaging diagnostic to determine the magnetic field profile. The design of this interferometer is motivated by the cyclic shearing interferometer presented in previous work [1]. Unlike traditional interferometry designs, the probe beam is split after traversing through the plasma to accommodate fielding constraints unique to the Z Machine. One portion of the beam is magnified through a telescope, which will have a relatively planar wavefront compared to the probe beam and can be utilized as a reference beam for interference. The beams are then re-combined at a manipulable angle to provide flexibility in fringe spacing and thickness. The layout of this interferometer is presented in the poster. This system will be initially tested on the Mykonos Pulsed Power Accelerator prior to implementation on the Z Machine. Images collected from the interferometer will be post-processed to provide the spatially resolved line integrated electron density profile.



Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

[1] M. Tatarakis, et al., Phys. Plasmas 5, 682–691 (1998), Optical probing of Fiber Z-pinch plasmas.