Qualification of a high-efficiency, gated spectrometer for x-ray Thomson scattering on the National Ignition Facility

Abstract

We have designed, built, and successfully fielded a highly efficient and gated Bragg crystal spectrometer for x-ray Thomson scattering measurements on the National Ignition Facility (NIF). It utilizes a cylindrically curved Highly Oriented Pyrolytic Graphite crystal. Its spectral range of 7.4-10 keV is optimized for scattering experiments using a Zn He-α x-ray probe at 9.0 keV or Mo K-shell line emission around 18 keV in second diffraction order. The spectrometer has been designed as a diagnostic instrument manipulator-based instrument for the NIF target chamber at the Lawrence Livermore National Laboratory, USA. Here, we report on details of the spectrometer snout, its novel debris shield configuration and an in situ spectral calibration experiment with a Brass foil target, which demonstrated a spectral resolution of E/ΔE = 220 at 9.8 keV.

Improving a high-efficiency, gated spectrometer for x-ray Thomson scattering experiments at the National Ignition Facility

“…In these measurements the MACS spectrometers are looking at the foils under a small glancing angle to reduce the source size to 200 µm in the dispersive direction. 7 Compared to Ref. 7 we reduced the Al filtering in front of the MCP detector from 900 to 600 µm to enhance the line emission over the high-energy continuum background that is reflected in second diffraction order.…”

“…7 Compared to Ref. 7 we reduced the Al filtering in front of the MCP detector from 900 to 600 µm to enhance the line emission over the high-energy continuum background that is reflected in second diffraction order. Table I summarizes the MACS calibration measurements with HOPG in first order that have been conducted to date.…”

“…3,4 We are developing XRTS for spherical implosion experiments at the National Ignition Facility (NIF). [5][6][7][8][9] In this paper we focus on reporting on further improvements to the Mono Angle Crystal Spectrometer (MACS), which is a highcollection efficiency, gated x-ray spectrometer for XRTS with Zn He α line emission at 9 keV at the NIF. 7 The initial MACS design used a cylindrically curved HOPG (highly oriented pyrolytic graphite) crystal, which focuses the x-rays in the nondispersive axis.…”

“…[5][6][7][8][9] In this paper we focus on reporting on further improvements to the Mono Angle Crystal Spectrometer (MACS), which is a highcollection efficiency, gated x-ray spectrometer for XRTS with Zn He α line emission at 9 keV at the NIF. 7 The initial MACS design used a cylindrically curved HOPG (highly oriented pyrolytic graphite) crystal, which focuses the x-rays in the nondispersive axis. This provides high collection efficiency and crude spatial resolution along the non-dispersive axis, which enables spatial discrimination of possible background signals.…”

“…1(a) in Ref. 7). In order to maintain the same dispersion across different crystals, the absolute height in the dual cylinder crystal surface is set such that the valleys are at the same normal distance to the symmetry line (source to detector) of 54 mm as in the single cylinder case.…”