Neutrinoless double beta decay. Annual progress report, January 1, 1984-December 31, 1984

Work is continuing on a collaborative experiment with experimenters from the Lawrence Berkeley Laboratory to search for neutrinoless double beta decay in Mo100. We have developed a hybrid, lithium drifted, silicon surface barrier detector 1.5 mm thick and 7.1 cm in diameter which, operating at LN2 temperature and in conjunction with an Amptek A225 low noise preamplifier and amplifier chip, gives an electronic resolution of 18 keV FWHM. At present, we have 8 working detectors of this type and another 8 currently being fabricated, and we expect to have between 50 and 70 of these detectors working by January 1985. We have also fabricated 5 grams of isotopically pure Mo100 into 7 micron thick circular foils 7.1 cm in diameter and have constructed a titanium cryostat with an oxygen-free, high conductivity electrolytic (OFHC) copper dipstick which currently contains a stack of 6 detectors and is being used to evaluate backgrounds from the residual natural radioactivity remaining in the detector system. We hope to begin taking data with 5 to 10% of the full array by early 1985