High Resolution X-Ray Spectrometer for Precision EXAFS Measurements in the 6 keV to 15 keV Energy Range

Published

July 29, 2016

Author(s)

Lawrence T. Hudson, John F. Seely, Albert Henins, Uri Feldman

Abstract

A Cauchois transmission-crystal spectrometer has been developed with high crystal resolving power in the 6 keV to 15 keV energy range and sufficient sensitivity to record single-shot spectra from the LLNL Titan laser and other comparable or more energetic lasers. The spectrometer capabilities were tested by recording the W L transitions from a laboratory source and the extended x-ray absorption fine structure (EXAFS) spectrum through a Cu foil. The spectrometer utilized a quartz crystal that was cut with the (100) planes perpendicular to the crystal surface that faced the source. The optical design employed asymmetric diffraction by the (302) planes that are at an angle of 27.69o from the (100) planes (and from the normal to the crystal surface). The intrinsic crystal broadening near the 8980 eV Cu K edge, determined by fitting Voigt profiles to the W L lines and removing the natural (lifetime) Lorentzian broadening and the TR image plate broadening, was Gaussian in shape with 1.9 eV FWHM resulting in 4,700 intrinsic crystal resolving power. The distance parameter of the nearest-neighbor Cu atoms from the absorbing atom was derived from the Cu EXAFS spectrum, and the value 2.19 ± 0.10 Å was in agreement with the synchrotron-based measurement of 2.25 Å. The laboratory exposure time was comparable to other Cauchois spectrometers that have recorded single-shot spectra at the Titan and other comparable lasers. This work demonstrates the capability to record detailed single-shot EXAFS spectra in the 6 keV to 15 keV range, and to thereby determine the electron temperature and density in compressed warm dense matter, using a relatively small instrument footprint (0.5 m in length) and small standoff distance (25 cm or less) that are compatible with laser experimental vacuum chambers and instrument insertion modules

Proceedings Title

Topical Conference on High-Temperature Plasma Diagnositics

Issue

87

Conference Dates

June 19-24, 2016

Conference Location

Madison, WI

Pub Type

Conferences

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DOI Link

Keywords

EXAFS, high resolving power, x-ray spectroscopy

Citation

Hudson, L. , Seely, J. , Henins, A. and Feldman, U. (2016), High Resolution X-Ray Spectrometer for Precision EXAFS Measurements in the 6 keV to 15 keV Energy Range, Topical Conference on High-Temperature Plasma Diagnositics, Madison, WI, [online], https://doi.org/10.1063/1.4959918 (Accessed March 20, 2025)