Astronomy at photon energies above 10 keV is severely limited by the poor signal to noise ratios achievable with present instrumentation. This situation can only be significantly improved by the development of flux concentrating devices for hard X-rays. The feasibility of a concentrator for 511 keV X-rays based on Bragg reflections from high quality metal crystals has been studied theoretically and through laboratory measurements on sample crystals. Order-of-magnitude gains in sensitivity coupled with source localiza-tions at the 10-arcsecond level are predicted for such a Bragg-telescope. The price paid for relying on Bragg reflections is that the telescope sensitivity may have to be concentrated in a sequence of separated energy bands and that the field of view of the telescope is very limited - only a few square arcminutes.
Niels Lund, Niels Lund,
"Improving the Signal to Noise Ratio in Hard X-Ray Astronomy", Proc. SPIE 0597, X-Ray Instrumentation in Astronomy, (14 July 1986); doi: 10.1117/12.966575; https://doi.org/10.1117/12.966575