Dubovik O. Obtaining of ZnWO4, MgWO4 crystal scintillators and solid solutions (Zn,Mg)WO4

The work is devoted to obtaining of high efficient inorganic scintillation crystals ZnWO4, MgWO4 and solid solutions (Zn,Mg)WO4. Structure, luminescent, and scintillation properties of the obtained crystals have been studied. ZnWO4 crystal scintillators of large volume (up to ∅55×150mm) with advanced scintillation properties and reasonable mechanical characteristics were developed. It was achieved thanks to optimization of growth conditions and initial composition by doping ZnWO4 charge with metals of the first and second groups, as well as by elements with high electric negativity. The best one-centimeter samples shown energy solution at the level of 8,5 % for 662 keV γ line of 137Cs. Low level of afterglow (0.002%, 20 ms after excitation) was obtained with one of ZnWO4 scintillators. Developed a technique for the growing MgWO4 crystals by pulling a seed from the melted flux solution, and used this to produce ≥ 1 cm3 crystals of good optical quality. The optical and scintillation properties of this new crystal scintillator were systematically studied for the first time. The crystal shows a broad emission band with a maximum at 470 nm under X-ray excitation. The afterglow of the crystal is found to be 0.035% 20 ms after termination of X-ray excitation. The relative photoelectron output was found to be 35% that of CdWO4. The relative intensity and scintillation decay kinetics were investigated over the temperature range 7–305 K. The relative scintillation efficiency of MgWO4 is found to be ⁓33 % that of ZnWO4 at T = 7 K. These results demonstrate that MgWO4 has a good prospect as a scintillation detector for particular applications, such as rare event searches that require a range of different cryogenic scintillators. Mixed crystals (Zn,Mg)WO4 were first grown by the Czochralski method. Structure, luminescent, and scintillation properties of the obtained mixed crystals have been studied. It is shown that the light output of ZnxMg1-xWO4 solid solutions has a maximum at x = 0,5 under X-ray excitation. Presented results allow to consider (Zn,Mg)WO4 as a new and promising scintillating material. Keywords: single crystal, zinc tungstate, magnesium tungstate, solid solution, Czochralski method, optical properties, scintillator, light output,