Our group operates a high-purity germanium (HPGe) spectrometer
 in a low-background environment underground at LNGS, under an average overburden of 3600 mwe.  Gamma-ray spectroscopy is a standard method to screen and select materials for rare-event searches. Our germanium spectrometer (Gator) is placed in a low-background shield and combines a high energy resolution with a very low intrinsic background.

Gator is one of the world's most sensitive HPGe detectors, with an integral counting rate of about 7.5 events/hour in the energy region 100-2700 keV. It can detect sample activities down to about 10 microBq/kg for ²²⁶Ra and ²²⁸Th/²²⁸Ra. The detector was used to screen XENON and GERDA/LEGEND detector and shield components for their U/Th/K/Co content. In particular, it was employed to develop, together with Hamamatsu, VUV-sensitive PMTs with very low radioactivity levels. Furthermore, it was employed in the  material radioassay and selection campaign for the XENON1T
and XENONnT experiment, respectively. The results were used to construct full background models of the existing experiments and are guiding the construction of future experiments.  Currently, radioassay of potential materials for the DARWIN experiment, as well as for LEGEND-1000, is ongoing. Recently, Gator has further been employed to perform high-precision experimental searches for possible small violations of the Pauli Exclusion Principle.

The detector contains a 2.2 kg p-type HPGe crystal housed in an electro-refined copper cryostat. It is surrounded by shields made of low-activity copper, lead and polyethylene and is housed in a box permanently flushed with pure nitrogen gas to suppress the influx of ²²²Rn. The sample chamber has a dimension of about (25x25x30) cm³, allowing us to place rather large samples around the germanium diode.