Research and Development of ZnBO₄(B = W, Mo) Crystal Scintillators for Dark Matter and Double Beta Decay Searching

Abstract

Oxide crystal scintillators play a considerable role in fundamental and applied researches. However, working out of new generation of high-sensitivity equipment and new methods of research puts higher requirements. The ZnBO 4 (B = W, Mo) crystals were grown from charge in platinum crucibles with high frequency heating, using the Czochralski method. The raw powder with optimum composition was prepared by solid phase high temperature synthesis using ZnO and BO 3 (B = W, Mo) with 4-5N purity. Single crystals with sizes up to 50 × 100 mm were grown and scintillation elements of various sizes and shapes (cylinders, rectangular and hexahedron prisms) were produced. High spectrometric characteristics were obtained for ZnWO 4 : R = 8-10% under excitation by 137 Cs (E γ = 662 keV), low radiation background (less than 0.2 mBq/kg) and low afterglow (0.002%, 20 ms after excitation). The obtained results demonstrate good prospects for ZnWO 4 and ZnMoO 4 crystal scintillators for application in low-count rate experiments, searching for double beta decay processes, interaction with dark matter particles, and also studies of rare decay processes. The material has also a good potential for application in modern tomography, scintillation bolometers and for other major researches using scintillators.

Growth and characterization of isotopically enriched 40Ca100MoO4 single crystals for rare event search experiments

“…The Czochralski technique is a universal method commonly used in the production of high-quality tungstates and molybdates [10,11,13,14]. The melting temperature of CaMoO 4 (T=1445 °C) permits pulling the crystals in air atmosphere using a crucible made of platinum (T melt = 1769 °C) or in an oxygen-free atmosphere using an iridium crucible (T melt = 2454 °C).…”

“…Within the range of inorganic Mo-containing materials, CaMoO 4 shows relatively bright scintillation at room temperature [7]. Other molybdates of the AMoO 4 family either exhibit practical scintillation only upon cooling (PbMoO 4 , SrMoO 4 , CdMoO 4 ) [7][8][9][10] or ____________________ remain fairly dull (MgMoO 4 , ZnMoO 4 ) [7,11,12]. This motivated the development of calcium molybdate scintillators for the 0νDBD experiment that has been initiated by some of the authors a few years ago.…”

Effect of the surface on luminescence properties of ZnWO4 crystals

“…The studied ZnWO 4 solid-phase method using Zn and W oxides (99.995 mass%) as starting materials [13].…”

Purification of molybdenum oxide, growth and characterization of medium size zinc molybdate crystals for the LUMINEU program

“…The cut-off wavelengths are 313 nm ( 3.96 eV) and 5.13 m. The absorption coefficient decreases from 1.47 to 0.89 cm -1 in the wavelength region from 400 nm to 2 m, but there does not seem to have a broad absorption band around 440 nm that could be ascribed to Fe 2+ /Fe 3+ impurities as described in [21] and [22]. This is due to the low Fe concentration in the crystal ( 1.7110 16 cm -3 ) and in fact, it can be stated that a safe detection limit around 440 nm by such transmission experiments is ~ 10 18 atoms of Fe per cm 3 .…”