The COBRA Experiment Annual Report 2017 The COBRA collaboration

The aim of the COBRA experiment (Cadmium Zinc Telluride 0-Neutrino DoubleBeta Research Apparatus) is to search for the existence of neutrinoless double beta-decay (0νββ-decay) and to measure its half-life. The COBRA demonstrator at LNGS is used to investigate the experimental issues of operating CZT detectors in low background mode while additional studies are proceeding in surface laboratories. The current demonstrator consists of 64 monolithic, calorimetric detectors in a coplanar grid (CPG) design. These detectors are 1×1×1 cm3 in size and are operated in an array of 4×4×4 crystals. As a semiconductor material, CadmiumZinc-Telluride (CdZnTe or simply CZT) offers the low radioactivity levels and good energy resolution required for the search for 0νββ-decay. Furthermore, CZT naturally contains several double beta-decay candidates. The most promising is 116Cd with a Q-value of 2.8 MeV, which lies above the highest prominent γ-line occurring from natural radioactivity. In 2017 the main research activity aimed to upgrade the experiment to the so-called eXtenden DEMonstrator COBRA XDEM.