Development of a New Type of Germanium Detector for Dark Matter Searches

A new type of germanium (Ge) detector for dark matter searches is under development utilizing the Ge crystal growth facility recently established at the University of South Dakota. Detector-grade crystals with electric impurity levels within 1010/cm3 and neutral impurity levels within 1014/cm3 have been grown regularly in the laboratory. These crystals can be fabricated into planar detectors with 1cm in thickness and 10cm in diameter. When a high voltage is applied to one of the end planes, a uniform electric field in the volume can be established. Such a design could result in a very fast electric signal. A time resolution of 1ns is expected by combining a short drift length and large drift mobility. This may allow us to resolve the difference on the electric pulse rise-time between low-energy nuclear recoil events and electronic recoil events at liquid nitrogen temperatures. An array of 168 planar detectors of this kind was modeled in a Geant4-based Monte Carlo simulation package. Its background reduction power was investigated and its sensitivity in dark matter search is estimated to be ~10-48cm2.