Design of a Multi-Monochromatic X-ray Imager (MMI) for Kr K-shell line emission

• Published in: Review of scientific instruments Vol. 93; no. 11; pp. 113525 - 113530
• Main Authors: Gallardo-Diaz, E., Mancini, R. C., Cliche, D. T., Tommasini, R.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 01.11.2022; American Institute of Physics (AIP)
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Algorithms; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Electron energy; Multilayers; Photons; Ray tracing; Spatial distribution; Spectral resolution; Spectroscopy
• ISSN: 0034-6748; 1089-7623; 1527-2400; 1089-7623
• DOI: 10.1063/5.0101862

The Multi-Monochromatic X-ray Imager (MMI) is a time-gated spectrometer used in implosion experiments at the OMEGA laser facility. From the data, electron temperature and density spatial distributions can be obtained at different implosion times. Previous MMI designs used Ar K-shell emission (3–6 keV) as a spectroscopic tracer and provided a spectral resolution of around 20 eV. However, Ar K-shell line emission becomes less useful at electron temperatures above 2 keV due to over-ionization. Kr K-shell (12–16 keV) has been shown to be an attractive alternative to diagnose hot implosion cores in recent publications. The purpose of this paper is to show a new point design that allows the MMI to detect this higher photon energy range with suitable spectral resolution. The algorithm used to find the optimal design couples a ray-tracing code and an exhaustive parameter space search. This algorithm may be useful as a tool to find optimal MMI designs for other purposes, i.e., other spectral regions for other spectroscopic tracers. The main change between the two designs is the replacement of the multi-layer mirror with a flat Bragg Ge (220) crystal. The final Kr K-shell MMI design has a photon energy range from 12 to 16.1 keV.