Investigation on intrinsic alpha-particle events in CdZnTe detectors

Orateur : F. KANDZIA (Technical University of Dresden)

Double beta decay is one of the rarest known processes in nature, with a half-life in the range of 1020 years in the neutrino accompanied case. If neutrinos are Majorana particles instead of Dirac particles this decay can also occur neutrinoless, with expected half-lives around 1026 years. The task of the C0BRA experiment is to search for this neutrinoless decay. For this purpose room temperature semiconductor detectors made of CdZnTe are used, which serve as detectors as well as a source of the main isotope Cd-116. To achieve the required sensitivity for these long half-lives, it is necessary to strongly suppress the background. Beside extensive shielding, pulse shape analysis is used for this purpose. For some events in the region of interest it is expected to be caused by alpha decays within the detectors. For that reason it was investigated whether some characteristic pulse shapes of such alpha events could be identified. Therefor a running detector was irradiated with neutrons from the neutron generator of the Technical University of Dresden, to obtain intrinsic (n,α) and (n,p) reactions which then can be analysed. In preparation for these studies the angular dependence of the neutron field of the generator had to be characterised, this was achieved by use of activation foil measurements. These measurements were carried out twice, one time before some larger deconstruction works in the neutron hall and one time afterwards, in order to check if the neutron field has been changed. In this talk I will give a a short introduction to double beta decay and the C0BRA experiment and will then present the methods used in my diploma thesis as well as the achieved results.

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