Phonon and Charge Signals from IR and X Excitation in the SELENDIS Ge Cryogenic Detector

The aim of the SELENDIS project within the EDELWEISS collaboration is to observe single e ^- h ^+ pairs in lightweight (3.3 g) cryogenic germanium bolometers with charge and phonon readout at biases up to ∼ 100 V. These devices are ideal to characterize in detail the mechanism of charge creation and collection in cryogenic germanium detectors. Electron–hole pairs are produced in the bulk of the detector either by the injection of pulsed IR laser or by neutron activation of germanium inducing the K , L and M lines from ^71 Ge electron capture decays. Low-energy laser pulses are also used to probe the single e ^- h ^+ pair sensitivity of Ge bolometers. Preliminary results are used to compare these two modes of charge creation, an important step toward a detailed characterization of Ge bolometers for their use in sub-MeV dark matter searches.