As sample sizes in a QC lab are very small we have chosen a High-Purity Germanium (HPGe) Well Detector providing high efficiency because the sample is virtually surrounded by active detector material.
The Well detector is fabricated with a blind hole, leaving at least 15 mm of active detector thickness at the bottom of the well and approaching a 4π counting geometry.
The Well insert in the endcap is made of aluminium with a side-wall thickness of 0.5 mm and a 1 mm thick bottom. The ion implanted contact on the detector element is negligibly thin compared to 0.5 mm of aluminium so these detectors have intrinsically good low energy response, allowing spectroscopy down to 20 keV.
Because germanium has relatively low band gap, these detectors must be cooled in order to reduce the thermal generation of charge carriers.