Improvement of the low gamma-energy response of great-volume Ge(Li) detectors by illumination with infrared light

Studies with low-energy gamma-radiation show a dead layer of a thickness of about 1 mm at the surface of the intrinsic region of Ge(Li) detectors. Predominantly due to hole trapping in dead layer, low-energy gamma-spectroscopy below 100 keV with great-volume high-resolution Ge(Li) detectors is strongly degraded. A distinct improvement of the charge collection properties of the detector for low-energy gamma-quanta is achieved, when the intrinsic region is simultaneously illuminated with infrared light in the energy range of 0.69-0.82 eV. Consequently, utilizing this technique, it becomes possible to use great-volume Ge(Li) detectors for gamma-spectroscopy down to energies of about 30 keV. (orig.)