Low-background experiment to search for double beta decay of 106Cd using 106CdWO4 scintillator

An experiment to search for 2epsilon, epsilonbeta+ and 2beta+ decays of 106Cd, using a 215 g cadmium tungstate scintillation crystal enriched at 66 % by 106Cd (106CdWO4) is carried out at the Gran Sasso underground laboratory (Italy). Events in the 106CdWO4 detector are recorded in (anti)coincidences with two large-volume CdWO4 scintillation counters. The design of the detector system, calibration and background measurements, methods, and results of data analysis to determine key detector characteristics are described. The experimental data are compared with Monte Carlo simulation results, and a background model is constructed. The radioactive contamination of the setup components is studied. The sensitivity of the experiment approaches the level of theoretical predictions for the 2niepsilonbeta+ decay channel, while for other possible 2beta-decay channels it is already on the level of lim T_1/2 about 10^21 - 10^22 years.