A 0.9-?eV direct backscattering spectrometer for the 50 Hz target station of the European Spallation Source ESS

The instrument presented is a pulsed-source backscattering crystal-analyzer spectrometer for highest energy resolution at an extended range of momentum transfers. The secondary spectrometer, based on Si(111) crystal analyzers, provides an energy resolution of 0.9 μeV. A second analyzer system using Si(311) crystals provides a more modest energy resolution of ∼6 μeV with an extended energy and Q range. The combination of high count rate, extended dynamic range in energy transfer along with the energy-resolution characteristics of classical reactor spectrometers results in a spectrometer that will be comparable with classical reactor-based backscattering spectrometers.