Performance of a prototype tracking detector for double beta decay measurements

To investigate double beta decay processes, the NEMO collaboration began a long-range research and development program in 1988. The NEMO 2 detector, which is now running in the Fréjus underground laboratory (L.S.M. Laboratoire Souterrain de Modane), is the second prototype. It consists of a 1 m2 source foil sandwiched between Geiger cell drift chambers for electron tracking and two plastic scintillator walls for energy and time-of-flight measurements. The technical description of the detector is followed by the study of the various sources of background.