Search for 2β processes in Zinc and Tungsten with ZnWO4 crystal scintillators
2011 - Search for 2β processes in 64Zn 70Zn, 180W, and 186W by using large volume (0.1 - 0.7 kg) low background ZnWO4 crystal scintillators has been performed. In particular
Four ZnWO4 crystal scintillators were used. Two crystals (117 g, 20 × 19 × 40 mm, and 699 g, 44 × 55 mm) were produced by the Czochralski method in the Institute for Scintillation Materials (Kharkiv, Ukraine). After 2130 h of low-background measurements, the crystal of 699 g was re-crystallized with the aim to study the effect of the re-crystallization on the radioactive contamination of the material. The third ZnWO4 crystal (141 g, 27 × 33 mm) was obtained by the recrystallization process and used in further measurements. The fourth ZnWO4 crystal scintillator (239 g, 41 × 27 mm) was produced in the Nikolaev Institute of Inorganic Chemistry (Novosibirsk, Russia) by the low-thermal gradient Czochralski technique. The radioactive contaminations of the used crystals have been measured.
The ZnWO4 crystal scintillators were fixed inside a cavity of 49 × 59 mm in the central part of a cylindrical polystyrene light-guide of 66 × 312 mm. The cavity was filled up with high purity silicone oil. The light-guide was optically connected on opposite sides by two low radioactivity PMTs. The detector was modified at the final stages of the experiment: two polished quartz light-guides (66 × 100 mm) were installed between the polystyrene light-guide and the PMTs to suppress gamma ray background from the PMTs. The detector has been installed in the low background DAMA/R&D set-up.