BROADCASTS.com

A detailed study of alpha interactions on the passivated surface of a germanium detector is\npresented. Germanium detectors can be used to search for both neutrinoless double beta\ndecay of 76Ge and direct interaction of dark matter. In order to increase the sensitivity to\nboth neutrinoless double beta decay and dark matter beyond the current state of the art,\nthe next generation of germanium-based experiments has to have a mass of about one ton\nand has to reduce the background by a factor of ten. The choices of detector technology\nfacilitating both searches and the background reduction are one of the biggest challenges\nfor such an experiment. Surface contaminations on the material close to the detectors or\non the detectors themselves, can generate a background due to alpha particles, which was\nfound to be limiting in some experiments.\nThe characterization of events induced by alpha particles will help to identify such\nevents and thus eliminate them as sources of background. An especially designed segmented\ntrue-coaxial detector was probed with alpha particles from an 241Am source inside the\ntest-stand GALATEA, located at the MPI f\xa8ur Physik in Munich. Pulse shape analysis was\nperformed to identify the characteristics of alpha events. The properties of the detector\ndirectly underneath the passivation layer on the end-plate were also studied. As part of\nthe detector characterization, the thickness of the effective dead layer was determined.\nThe studies presented here suggest improvements on detector design, which would\nallow an effective reduction of alpha background in next generation of germanium-based\nexperiments.