HAPG mosaic crystal Von Hamos spectrometer for high precision kaonic atoms spectroscopy

Abstract

Von Hamos (VH) spectrometers are widely used in several fields, ranging from pure physics applications to very different types of practical ones. However, these type of Bragg spectrometers are usally implied in high rate -high resolution experiments, where the typical source size can be as low as few tens of microns. These limitations prevented them to be used as X-ray detectors for high precision exotic atoms spectroscopy, except for cases where extremly high flux beams could be employed, like in the case of pionic atoms at PSI. Recently, we developed a VH spectrometer, within the VOXES collaboration at the INFN Laboratories of Frascati, making use of Highly Annealed Pyrolitic Graphite (HAPG) mosaic crystals and a X-ray beam optics optimization, which could be used for source sizes up to few mm, (in the Bragg plane), some tens of mm in the sagittal plane and, if gaseous sources are used, of several tens of cm in the X-ray propagation direction. Such kind of a spectrometer could be used, for example, to open a new era in the field of exotic (kaonic) atoms precision measurements, delivering data with unprecedented precision to the (strangeness) nuclear physics community. In this paper we present, together with an overall description of the VOXES spectrometer and of its main characteristics in terms of resolution and efficiencies, a comparison between a kaonic helium 3 → 2 transition spectrum measured with Silicon Drift Detectors and ray tracing simulated spectra of how the same transition would appear if measured with our apparatus.