This proposal is for the continuation of support for development of a large 6 crystal ultralow background Ge spectrometer, and its installation in the Homestake goldmine. The detector will be used for a sensitive search for all modes of the double beta decay of Germanium-76. An essential feature of the detector is reduced background due to contaminants. Primordial contaminants have been reduced by more than three orders of magnitude. New sources of background have also been removed. The data from the present ultralow background prototype detectors have been combined with other data to place a limit of 4x1023yr. for the neutrinoless double beta-decay of Germanium-76, corresponding to a neutrino mass less than 2.4eV using the shell model nuclear structure calculations. Although this limit has recently been surpassed by the Santa Barbara/LBL group, the present detector, which was specially deep mined and is very low in cosmogenic radioactivity (below 0.2 counts/keV/yr/kg), will permit further reductions in that limit. The low energy portion of the data from the prototype was used to place limits on the mass and couplings of dark matter candidates and on the coupling of DFS solar axions to electrons. Finally, an anomalous bump was discovered in the spectrum of the low background prototype, which was suggestive of neutrinoless double beta-decay with a massless or almost massless particle. This exciting possibility, which cannot be confirmed or refuted with other Germanium-76 experiments because the best ones still have more background in a critical region of the spectrum, will be explored in a new improved experiment.
