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Radioactive contamination of ZnWO4 crystal scintillators

Authors :: Belli, P.
Bernabei, R.
Cappella, F.
Cerulli, R.
Danevich, F. A.
Dubovik, A. M.
d'Angelo, S.
Galashov, E. N.
Grinyov, B. V.
Incicchitti, A.
Kobychev, V. V.
Laubenstein, M.
Nagornaya, L. L.
Nozzoli, F.
Poda, D. V.
Podviyanuk, R. B.
Polischuk, O. G.
Prosperi, D.
Shlegel, V. N.
Tretyak, V. I.
Tupitsyna, I. A.
Vasiliev, Ya. V.
Vostretsov, Yu. Ya.
Source :: Nucl. Instrum and Meth. A 626 (2011) 31
Publication Year :: 2010
Abstract: The radioactive contamination of ZnWO4 crystal scintillators has been measured deep underground at the Gran Sasso National Laboratory (LNGS) of the INFN in Italy with a total exposure 3197 kg x h. Monte Carlo simulation, time-amplitude and pulse-shape analyses of the data have been applied to estimate the radioactive contamination of the ZnWO4 samples. One of the ZnWO4 crystals has also been tested by ultra-low background gamma spectrometry. The radioactive contaminations of the ZnWO4 samples do not exceed 0.002 -- 0.8 mBq/kg (depending on the radionuclide), the total alpha activity is in the range: 0.2 - 2 mBq/kg. Particular radioactivity, beta active 65Zn and alpha active 180W, has been detected. The effect of the re-crystallization on the radiopurity of the ZnWO4 crystal has been studied. The radioactive contamination of samples of the ceramic details of the set-ups used in the crystals growth has been checked by low background gamma spectrometry. A project scheme on further improvement of the radiopurity level of the ZnWO4 crystal scintillators is briefly addressed.<br />Comment: 15 pages, 8 figures, 6 tables, submitted for publication