Monte Carlo study of detector concepts for the MAX Laue lens gamma-ray telescope

Abstract

Abstract. MAX is a proposed Laue lens gamma-ray telescope taking advantage of Bragg diffraction in crystals to concentrate incident photons onto a distant detector. The Laue lens and the detector are carried by two separate satellites flying in formation. Significant effort is being devoted to studying different types of crystals that may be suitable for focusing gamma rays in two 100 keV wide energy bands centered on two lines which constitute the prime astrophysical interest of the MAX mission: the 511 keV positron annihilation line, and the broadened 847 keV line from the decay of 56 Co copiously produced in Type Ia supernovae. However, to optimize the performance of MAX, it is also necessary to optimize the detector used to collect the source photons concentrated by the lens. We address this need by applying proven Monte Carlo and event reconstruction packages to predict the performance of MAX for three different Ge detector concepts: a standard coaxial detector, a stack of segmented detectors, and a Compton camera consisting of a stack of strip detectors. Each of these exhibits distinct advantages and disadvantages regarding fundamental instrumental characteristics such as detection efficiency or background rejection, which ultimately determine achievable sensitivities. We conclude that the Compton camera is the most promising detector for MAX in particular, and for Laue lens gamma-ray telecopes in general.

Low Energy INTEGRAL Positrons from eXciting Dark Matter

“…In particular, the 10 43 e + /s concentrated in the galactic center region, as well as the highly spherical morphology are a challenge to achieve from most galactic sources, which tend to trace the disk. Alternative explanations, such as low mass X-ray binaries (LMXBs) [11] could possibly provide a candidate [12], although no point source 511 keV emission has yet been observed [13]. Likewise, it has been suggested that the transport of the positrons produced in the galactic disk into the galactic center could provide the rate [14], although the precise dynamics that achieves this and yields such a spherical morphology is unclear.…”

Simulated Performance of CZT-Based Focal Plane Detectors for Gamma-Ray Lenses

“…In addition, the fine voxelization would enable the selection of events from the core of the focal spot on the detector, which are more likely non-background events. In [4] and [5] it has been shown that voxel based (Compton) detectors outperform simple monolithic detectors. Therefore only those are considered in the following analysis.…”

“…The focal planes vary widely in size and complexity as well as in shielding approach. Each focal plane is placed on top of a generic spacecraft model [4].…”

Soft gamma-ray optics: new Laue lens design and performance estimates

“…We shall precise that the performance of Laue lens telescopes could even be enhanced if a Compton telescope is put at the focus. 15 It this case it has been shown that the background rejection is improved leading to a sensitivity increased by a factor of two. On the other hand, if the first layers of the focal plane Compton camera are made of Silicon, it allows polarization measurement down to ∼ 100 keV.…”