Feasibility of using 3D CZT drift strip detectors for small Compton camera space missions

This feasibility study explores the possibility of using 3D CZT drift strip detectors developed by DTU Space in a small Compton camera payload, with the primary objective of technology demonstration. We have defined a scalable mass model for the payload, comprising eight 3D CZT drift strip detectors surrounded by CsI scintillator detectors for active shielding. The payload's angular resolution, effective area, and efficiency are evaluated through simulations of far-field monochromatic point sources. The instrument's sensitivity is assessed in a low Earth orbit background environment for nuclear line and continuum emission sources. With a 3σ point source sensitivity in the order of 10^-4 [ph/cm²/s], it is evident that such an instrument only allows for limited scientific goals. In-orbit simulations of bright sources are conducted, resulting in reasonable observation times for the Crab Nebula at a 5σ significance level. Furthermore, in-orbit simulations of a selection of bright gamma-ray bursts indicate the potential for observing bright transient events. The study underscores the potential of using 3D CZT drift strip detectors in Compton camera configurations but also highlights the need for a larger effective area to improve sensitivity. However, for a technology demonstration aimed at increasing the Technology Readiness Level of the 3D CZT drift strip detector, a small Compton camera configuration like the one presented in this study could be a viable solution.