J. W. Beeman, F. Bellini, S. Capelli, L. Cardani, N. Casali, I. Dafinei, S. Di Domizio, F. Ferroni, E. N. Galashov, L. Gironi, F. Orio, L. Pattavina, G. Pessina, G. Piperno, S. Pirro, V. N. Shlegel, Ya. V. Vasilyev, C. Tomei, M. Vignati
We investigate the performances of two ZnMoO4 scintillating crystals operated
as bolometers, in view of a next generation experiment to search the
neutrinoless double beta decay of Mo-100. We present the results of the alpha
vs beta/gamma discrimination, obtained through the scintillation light as well
as through the study of the shape of the thermal signal alone. The
discrimination capability obtained at the 2615 keV line of Tl-208 is 8 sigma,
using the heat-light scatter plot, while it exceeds 20 sigma using the shape of
the thermal pulse alone. The achieved FWHM energy resolution ranges from 2.4
keV (at 238 keV) to 5.7 keV (at 2615 keV). The internal radioactive
contaminations of the ZnMoO4 crystals were evaluated through a 407 hours
background measurement. The obtained limit is < 32 microBq/kg for Th-228 and
Ra-226. These values were used for a Monte Carlo simulation aimed at evaluating
the achievable background level of a possible, future array of enriched ZnMoO4
crystals.
View original:
http://arxiv.org/abs/1202.0238
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