Monte-Carlo based background studies for the COBRA Experiment

COBRA is a next-generation experiment searching for neutrinoless double beta decay using CdZnTe semiconductor detectors. The main focus is on Cd-116, with a decay energy of 2814 keV well above the highest naturally occurring gamma lines. The concept for a large scale set-up consists of an array of CdZnTe detectors with a total mass of 420 kg enriched in 116Cd up to 90 %. With a background rate in the order of 10-3 counts/keV/kg/year, the experiment would be sensitive to a half-life larger than 1026 years, corresponding to a Majorana mass term mββ smaller than 50 meV. The broad R and D program encompasses many different activities, such as a test set-up at LNGS, able to house upto 64 CPG detectors with a size of 1 cm3. At the moment 16 detectors are running with a new FADC readout. Because of a high half-life, the background has to be reduced significantly. Background sources are for example neutrons, natural decay chains and the 2νββ decay. Besides the development of a shielding, the effects of different background sources are studied based on Monte-Carlo simulations. In the talk the current status of the Monte-Carlo survey is presented and discussed.