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

• Published in: Review of scientific instruments 2014-09, Vol.85 (9), p.093106-093106
• Main Authors: Zastrau, Ulf, Fletcher, Luke B, Förster, Eckhart, Galtier, Eric Ch, Gamboa, Eliseo, Glenzer, Siegfried H, Heimann, Philipp, Marschner, Heike, Nagler, Bob, Schropp, Andreas, Wehrhan, Ortrud, Lee, Hae Ja
• Format: Article
• Language: English
• Subjects: ANNEALING; Blurring; Coherent light; Coherent scattering; CRYSTALS; ENERGY RESOLUTION; EV RANGE; FREE ELECTRON LASERS; GALLIUM ARSENIDES; GRAPHITE; INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; LIGHT SOURCES; LINEAR ACCELERATORS; PYROLYTIC CARBON; Pyrolytic graphite; Rangefinding; REFLECTION; Scientific apparatus & instruments; Wavelengths; X RADIATION; X ray spectra; X ray spectrometers; X-RAY DIFFRACTION; X-ray scattering
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/1.4894821

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.