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Project Title: Cylindrically bent analyzer crystals for Nickel K-beta XES Spectroscopy

SLAC Staff Leland B. Gee Roberto Alonso-Mori

Description Currently at the LCLS we use Si(551) crystals with a 500 mm radius of curvature to measure Ni K-beta XES spectra. This spectroscopy strongly reports on the oxidation and spin state of nickel atoms by coupling of the 3p final state hole to the 3d-orbital manifold. Our current crystals are suboptimal as our users and staff have generally agreed that the gain in solid angle of 250 mm radius of curvature crystals is worth the minimal loss in energy resolution.

Project Scope and Plan Here we propose to purchase 6xSi(551) crystals with a 250 mm radius for user and staff use in our von Hamos spectrometers to collect Ni K-beta XES spectra.

Six crystals are required as our new MFX von Hamos spectrometer in development has 6 mounts for crystals (compared to our other spectrometers that have 4). Therefore, we want the option to maximize measurements with that spectrometer. The crystals must have a good spectral overlap and reflectivity;

thus, we anticipate them to have a 250 mm +-2 mm radius of curvature with the Si substrate <200 um thick. The form factor of the crystals required for the spectrometer require 110 mm x 25 mm for the crystals on their quartz/glass substrates.

These crystals would need to be available before the start of LCLS run 22 so we anticipate a delivery date on or before June 2023 to be optimal.