Efficiency measurements and simulations of a HAPG based Von Hamos spectrometer for large sources

In this paper we report about the reflection efficiency measurements of the VOXES Von Hamos (VH) spectrometer, based on HAPG mosaic crystals, together with the ray tracing simulations results. Von Hamos spectrometers are widely used in several fields, ranging from fundamental physics to various practical applications. These types of Bragg spectrometers are usually used in high rate – high resolution experiments, where the typical source size can be as low as few tens of microns. The VOXES collaboration at the INFN Laboratories of Frascati recently developed a VH spectrometer, making use of HAPG mosaic crystals and an optimized X-ray beam optics, which could be used for source sizes up to few mm, (in the Bragg plane) and some tens of mm in the sagittal plane. Such spectrometer may open a new era in the field of exotic (kaonic) atoms precision measurements, delivering data with unprecedented precision to the nuclear physics community. In order to plan the use of this spectrometer the capabilities in terms of signal collection efficiency need to be checked, reliable ray tracing simulations have to be developed and consistency between data and simulations has to be verified. In this paper, we present this crosscheck for a ρ = 206.7 mm cylindrically bent HAPG crystal using CuKα1;2 and FeKα1;2 XRF lines. For both of them, the experimental results and the simulations are found to be well in agreement within the errors.