High-Resolution Gamma-Ray Detection Using Phonon-Mediated Detection
The recent breakthroughs in hard X-ray/soft gamma-ray optics, as characterized by the NuSTAR (2011 launch) and NEXT (2013 launch) missions, have finally opened up the 10- 100 keV band to detailed astronomical observation. Nuclear spectroscopic techniques at these energies allow for further study of the dynamics of supernovae, a poorly understood phenomenon of great scientific relevance. Such a study would require an energy resolution of roughly 100 eV at 70 keV or 0.1%. The current state-of-the art in focal plane detectors, such as the CdZnTe detectors on NuSTAR, have a FWHM resolution of around 1 keV at 70 keV. I propose to develop new type of focal plane to recover this order of magnitude in sensitivity. The device will be an athermal phonon-mediated detector that uses the microwave kinetic inductance detector (MKID) technology currently being developed by JPL (Rick LeDuc, Peter Day, and Bruce Bumble) and Caltech (Jonas Zmuidzinas and Sunil Golwala). It will use a 2 mm thick Ge substrate to stop the gammas, and convert their energy to athermal phonons. These phonons travel in straight lines, preserving information about the interaction point. They would then be detected by MKIDS deposited on the surface of the substrate. We have fabricated a proof-of-concept, which has demonstrated an energy resolution of sigma = 1.16 keV at 30 keV.