Optical, luminescence and thermal properties of radiopure ZnMoO4 crystals used in scintillating bolometers for double beta decay search

D.M. Chernyak , F.A. Danevich , V.Ya. Degoda , I.M. Dmitruk , F. Ferri , E.N. Galashov , A. Giuliani (1) , I.M. Ivanov , V.V. Kobychev , M. Mancuso (1) , S. Marnieros (2) , V.M. Mokina , C. Nones (2) , E. Olivieri (3) , G. Pessina , C. Rusconi , V.N. Shlegel , O.P. Stanovyi , M. Tenconi (2) , V.I. Tretyak , I.A. Tupitsyna

1 CSNSM PS1
2 CSNSM - Centre de Sciences Nucléaires et de Sciences de la Matière
3 CSNSM INSTR

Zinc molybdate (ZnMoO4) crystals are an excellent candidate material to fabricate scintillating bolometers for the study of neutrinoless double beta decay of 100Mo, provided that the crystal quality meets strict optical, thermal and radiopurity requirements. This paper addresses the characterization of improved crystalline samples grown by the low-thermal-gradient Czochralski technique. Transmittance measurements confirm significant improvement of the material with respect to previously developed samples. Luminescence properties (emission spectra, dependence of intensity on temperature, thermally stimulated luminescence and phosphorescence) have been studied under X-ray excitation from liquid-helium to room temperature. The index of refraction was measured in the wavelength interval 406-655 nm. Samples of ZnMoO4 crystals with masses of 5.07 g and 23.8 g were operated as scintillating bolometers at temperatures below 30 mK, with simultaneous detection of scintillation and heat signals, confirming an excellent alpha/beta rejection power. Background measurements allowed encouraging radiopurity level estimations. The light collection from ZnMoO4 scintillators was Monte Carlo simulated, analysing different crystal size, shape and surface properties and different photodetector sizes.

Mots clés: Double beta decay; 100Mo; Cryogenic scintillating bolometer; ZnMoO4 crystal

Domaines: Instrumentations et Détecteurs [physics.ins-det]

D.M. Chernyak, F.A. Danevich, V.Ya. Degoda, I.M. Dmitruk, F. Ferri, et al.. Optical, luminescence and thermal properties of radiopure ZnMoO4 crystals used in scintillating bolometers for double beta decay search. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2013, 729, pp.856-863. ⟨10.1016/j.nima.2013.07.088⟩. ⟨in2p3-00954573⟩