Bent crystal selection and assembling for the LAUE project

Abstract

For the first time, with the Laue project, bent crystals are being used for focusing photons in the 80-300 keV energy range. The advantage is their high reflectivity and better Point Spread Function with respect to the mosaic flat crystals. Simulations have already shown their excellent focusing capability which makes them the best candidates for a Laue lens whose sensitivity is also driven by the size of the focused spot. Selected crystals are Germanium (perfect, (111)) and Gallium Arsenide (mosaic, (220)) with 40 m curvature radius to get a spherical lens with 20 m long focal length. A lens petal is being built. We report the measurement technique by which we are able to estimate the exact curvature of each tile within a few percent of uncertainty and their diffraction efficiency. We also discuss some results.

Results of the simulations of the petal/lens as part of the LAUE project

“…The petal that is being built is made up of both GaAs(220) and Ge(111) crystal tiles. 2,10,11 The selection of the crystals and their characterization is presented in [12]. Here we report the final simulation and performance results of this lens petal and of a lens made of petals like that is being assembled of either Ge (111) or GaAs(220).…”