Bent crystal spectrometer for both frequency and wavenumber resolved x-ray scattering at a seeded free-electron laser

Ulf Zastrau; Luke B Fletcher; Eckhart Förster; Eric Ch Galtier; Eliseo Gamboa; Siegfried H Glenzer; Philipp Heimann; Heike Marschner; Bob Nagler; Andreas Schropp; Ortrud Wehrhan; Hae Ja Lee

doi:10.1063/1.4894821

Bent crystal spectrometer for both frequency and wavenumber resolved x-ray scattering at a seeded free-electron laser

Rev Sci Instrum. 2014 Sep;85(9):093106. doi: 10.1063/1.4894821.

Affiliations

¹ Institute of Optics and Quantum Electronics, Friedrich-Schiller University Jena, Max-Wien-Platz 1, 07743 Jena, Germany.
² Stanford Linear Accelerator Center (SLAC), 2575 Sand Hill Road, Menlo Park, California 94025, USA.

PMID: 25273706
DOI: 10.1063/1.4894821

Abstract

We present a cylindrically curved GaAs x-ray spectrometer with energy resolution ΔE/E = 1.1 × 10(-4) and wave-number resolution of Δk/k = 3 × 10(-3), allowing plasmon scattering at the resolution limits of the Linac Coherent Light Source (LCLS) x-ray free-electron laser. It spans scattering wavenumbers of 3.6 to 5.2/Å in 100 separate bins, with only 0.34% wavenumber blurring. The dispersion of 0.418 eV/13.5 μm agrees with predictions within 1.3%. The reflection homogeneity over the entire wavenumber range was measured and used to normalize the amplitude of scattering spectra. The proposed spectrometer is superior to a mosaic highly annealed pyrolytic graphite spectrometer when the energy resolution needs to be comparable to the LCLS seeded bandwidth of 1 eV and a significant range of wavenumbers must be covered in one exposure.