The Toroidal Slit Energy-Dispersive Diffractometer at CHESS

Abstract

We describe the design and performance of a novel instrument for energy dispersive X-ray diffraction (EDXRD). The instrument, coined a toroidal slit diffractometer (TSD), is based on a 23-element germanium detector with elements arranged in a semicircle and two pairs of variable-gap semicircular slits made from 6.6-mm thick tungsten plates. The working surfaces of the slits form a toroidal surface, permitting tunable scattering angle from 5 to 9^o and tunable slit size from <0 to 3 mm in the radial direction. The TSD was commissioned in the fall of 2023 at the Structural Materials Beamline (SMB) at the Materials Solutions Network at CHESS (MSN-C) for use with wiggler radiation spanning 40-200 keV. Here we describe the design features and performance of the TSD. We show that its key performance metrics, namely the uniformity of gauge volume size and position, are precisely accounted for by laser-based metrology of the four slits. We then highlight the performance of the new instrument by comparing strain maps obtained from nearly identical Ni-based superalloy samples using the TSD and the single-element system previously employed at SMB.