New results on focusing of gamma-rays with Laue lenses

ABSTRACT We report on new results on the development activity of broad band Laue lenses for hard X-/gamma-ray as-tronomy (70/100-600 keV). After the development of a “rst prototype, whose performance was presented at theSPIE conference on Astronomical Telescopes held last year in Marseille (Frontera et al. 2008), we have improvedthe lens assembling technology. We present the the development status of the new lens prototype that is on theway to be assembled.Keywords: Laue lenses, gamma-ray instrumentation, focusing telescopes, gamma-ray observations 1. INTRODUCTION Along with the hard X-ray astronomy up to 70/100 keV, also the gamma ray astronomy above this energy ismoving from direct sky-viewing telescopes to focusing tel escopes. With the advent of focusing telescopes in thisenergy range, a big leap is expected, i n both sensitivity and angular resolution. As far as the sensitivity isconcerned, the expected increase is by a factor of 100-1000 with respect to the best non-focusing instrumentsof the current generation (e.g., BeppoSAX/PDS, Ref. 1; INTEGRAL/IBIS, Ref. 2). Concerning the angularresolution, the increase is exp ected by more than a factor 10 (from 10 arcmin of the mask telescopes likeINTEGRAL IBIS to less than 1 arcmin). The next generation of gamma ray ( > 70/100 keV) focusing telescopeswill make use of the Bragg diraction technique from mosaic-like crystals in transmission con“guration (Lauelenses). The expected astrophysical issues that are exp ected to be solved with the advent of these telescopesare many and of fundamental importance. A discussion of them is done in the context of the mission proposalGamma Ray Imager (GRI), submitted to ESA in response to the “rst AO of the Cosmic Vision 2015 2025 plan(Ref. 3). For the astrophysical importance of the > 100 keV band, see also Refs. 3 6.Here we report on the status of our project HAXTEL (= HArd X-ray TELescope) devoted to developingthe technology for building Laue lenses with broad energy passband (70/100 600 keV). The results of thisdevelopment activity over the last few years have been reported and discussed (see Refs. 5,7 and referencestherein) with a summary of them given in Ref. 8.Last year we reported the “rst lens Prototype Model (PM ) and its performance (see Re f.8). Before discussingthe activity performed this year, we summarize the main f eatures of the assembly technique and the performanceof the “rst PM.