Time and Space Resolved Multi View X-Ray Spectroscopy at Z using Elliptical Crystal Spectrometers

Abstract

Summary form only given. X-ray spectrometers used in modern high energy density (HED) plasma experiments must provide high time, space, and spectral resolution while overcoming the difficulties imposed by the environment, including x-ray background, debris, and mechanical shocks. At the Z facility these problems are addressed using a suite of elliptical crystal spectrometers. The elliptical geometry isolates the detector from the line of sight with a slit placed at the elliptical focus, while the sensitivity enables locating the crystal 2-4 meters from the plasma source. Space and time resolution are obtained by using an array of slits to project a ID plasma image onto the crystal and recording the spectrally-dispersed image with a gated MCP detector. A spectrometer equipped with two crystals is used to double the number of time frames, enabling longer time durations to be spanned by a single instrument. Alternatively, the double crystal design allows simultaneous measurements with different crystals to investigate different spectral regimes. A spectrometer observing the plasma from a given direction suffers from a problem common to many HED plasma diagnostics: the data are integrated along the instrument line of sight, possibly leading to complications if the emitting plasma is non-uniform. This problem is being addressed at Z by deploying three separate spectrometers that observe the plasma from three almost-orthogonal directions. Multi-view measurements are common in relatively-large magnetic fusion plasmas, but have not been previously acquired in HED plasmas because of the need for simultaneous high spatial and temporal resolution. Spectra acquired from multiple views can provide information about the plasma symmetry from diverse experiments, including inertial confinement fusion capsule implosions and Z-pinch plasmas.