Operation of a high-purity germanium crystal in liquid argon as a Compton-suppressed radiation spectrometer

A high-purity germanium (HPGe) crystal was operated in liquid argon (LAr) as a Compton-suppressed radiation spectrometer. Spectroscopic quality resolution of less than 1% of the full-width half-maximum of full energy deposition peaks was demonstrated. The construction of the small apparatus used to obtain these results is reported. The design concept is to use the LAr bath to both cool the germanium crystal to operating temperatures and act as a scintillating veto. The scintillation light from the LAr can veto cosmic rays, external primordial radiation, and gamma radiation that does not fully deposit within the germanium crystal. This technique was investigated for its potential impact on ultra-low-background gamma-ray spectroscopy. This work is based on a concept initially developed for future germanium-based neutrinoless double-beta decay experiments.