Proposal for a Laue lens relying on hybrid quasi-mosaic curved crystals

¹ Department of Physics and Earth SciencesUniversity of Ferrara, via Saragat 1/c, 44122 Ferrara, Italy
² CNR – IDASC SENSOR Lab., Italy
e-mail: guidi@fe.infn.it

Received: 4 June 2013
Accepted: 11 October 2013

Abstract

A promising method of concentrating X- and soft γ-rays from celestial sources is a Laue lens. A new scheme for this lens, relying on diffraction in curved Si and Ge crystals, is introduced here. The proposed Laue lens is based on high-efficiency diffraction of curved (111) or (22$\overline{\mathrm{4}}$) crystalline planes, which are bent through quasi-mosaic effect. While diffraction in curved (111) quasi-mosaic crystals is well known and has recently been proposed for a Laue lens, diffraction by quasi-mosaic (22$\overline{\mathrm{4}}$) planes is suggested and demonstrated here through experimental work carried out at the Institut Laue-Langevin (ILL, Grenoble, France) at DIGRA, a facility specifically built for characterizing instrumentation in Astrophysics. Results show that the diffraction efficiency in the (22$\overline{\mathrm{4}}$) quasi-mosaic sample is amplified by more than one order of magnitude with respect to an equivalent crystal without quasi-mosaic effect. The lens has been designed in such a way as to maximize and smoothen its sensitivity, thanks to a custom-made code based on a genetic algorithm.