The ESA Flex instrument is designed to measure x-ray signals from custom, user-based sample designs that may include high pressure cells, cryo-cooled samples, or samples under controlled evironment, like gas feed or temperature. The instrument, based on the same as ESA prime von Hamos geometry, will be operated in-air with several degrees of freedom.
Based on synchrotron experience with user-defined sample setups, the spectrometer must also have capability to measure the x-ray emission or x-ray scattering signals at different scattering angles in respect to incoming x-ray beam. Moreover, either a horizontal or a vertical geometry have to be available, depending on the location of the exit windows from sample cell or sample chamber. Thus, in the ESA Flex setup the flexibility is a key parameter for spectrometer operation.
The spectrometer will be dedicated to measuring X-ray emission spectra in the range of 5 to 15 keV. The in-air von Hamos spectrometer will be designed for a 25 cm radius of curvature. This radius represents the best compromise for the requested operation characteristics (efficiency, resolution, space needed for operation). The spectrometer will work at Bragg angles between 90 and 50 degrees and will operate simultaneously with three diffraction crystals. For X-ray diffraction different types of crystals will be used, primarily Si(111), Si(110) and Si(100). The crystals will be used at different diffraction orders ((400), (800), (220), (440), (660), (333), (444), (555)) in order to cover the desired energy range. The setup will be based on segmented-type crystals prepared in-house at PSI. The expected energy resolution will be in the range of 0.1eV to 2eV depending on Bragg angle and diffraction order. The spectrometer will use a Jungfrau module as a detector.