A Scintillator-Based Hard X-Ray Imaging Telescope -- CASTER

The primary scientific goal of the Black Hole Finder Probe (BHFP) mission, a component of the NASA Beyond Einstein program, is to survey the local Universe for black holes over a wide range of mass and accretion rate. One approach to such a survey is a hard X-ray coded aperture imaging telescope operating in the 10 - 600 keV energy band, a spectral range especially useful for detecting black hole sources and studying their spectra. The development of new inorganic scintillator materials (e.g., LaBr3 and LaCl3) provides improved energy resolution and timing performance that is well suited to the BHFP science requirements. Detection planes formed with such materials coupled with a new generation of readout devices represent a significant advance in the performance capabilities of scintillator-based gamma cameras. We discuss the Coded Aperture Survey Telescope for Energetic Radiation (CASTER), a mission concept for a BHFP based on the use of the latest scintillator technology, and present laboratory test results demonstrating the expected scintillator performance. As part of NASA’s Beyond Einstein program, the Black Hole Finder Probe (BHFP) is designed to survey the local Universe for black holes over a wide range of mass and accretion rate. One approach to such a survey is a hard X-ray coded aperture imaging mission operating in the 10 - 600 keV energy band. The large detector area, high sensitivity, and directional resolution required for such a mission can be achieved at a reasonable cost with inorganic scintillators: New scintillator materials (e.g., LaCl3 and LaBr3) provide improved light output, energy resolution, and timing; new readout devices provide improved capabilities; and the use of segmented scintillators coupled to optical fibers promises to reduce the number of electronics channels and simplify the readout complexity. We describe the Coded Aperture Survey Telescope for Energetic Radiation (CASTER), a mission concept optimized to meet the BHFP science goals using an array of wide-field-of-view coded apertures with detection planes based on inorganic scintillators, and the technology developments that make CASTER possible. The task of a hard X-ray BHFP mission is to perform an all-sky census of black hole sources with a 1-year 5σ