Abstract
As proposed in the LUCIFER project, ZnSe crystals are attractive materials to realize scintillating bolometers aiming at the search for neutrinoless double beta decay of the promising isotope 82 Se. However, the optimization of the ZnSe-based detectors is rather complex and requires a wide-range investigation of the crystal features: optical properties, crystalline quality, scintillation yields and bolometric behaviour. Samples tested up to now show problems in the reproducibility of crucial aspects of the detector performance. In this work, we present the results obtained with a scintillating bolometer operated aboveground at about 25 mK. The detector energy absorber was a single 1 cm 3 ZnSe crystal. The good energy resolution of the heat channel (about 14 keV at 1460 keV) and the excellent alpha/beta discrimination capability are very encouraging for a successful realization of the LUCIFER program. The bolometric measurements were completed by optical tests on the crystal (optical transmission and luminescence measurements down to 10 K) and investigation of the crystalline structure. The work here described provides a set of parameters and procedures useful for a complete pre-characterization of ZnSe crystals in view of the realization of highly performing scintillating bolometers.
Highlights
The ZnSe is not an intrinsic scintillator; the luminescence is due to crystal imperfections, difficult to reproduce
Preliminary characterization is necessary: in this work we provide a series of useful procedures and parameters, having investigated the optical and structure properties of a crystal which exhibited excellent bolometric performances
Thermal signals from all the three absorbers were provided by technically identical 3×1×0.6 mm3 Neutron Transmutation Doped Ge thermistors (NTDs), whose resistivity is described by a law in Variable Range Hopping regime with Coulomb gap, ρ(T ) = ρ0 · exp (T0/T )0.5 where ρ0 = 1.09 Ω·mm and T0 = 3.83 K were determined in a previous characterization of the same Ge wafer
Summary
The ZnSe is not an intrinsic scintillator; the luminescence is due to crystal imperfections, difficult to reproduce. ZnSe absorbers are quite complex to characterize: in past tests, important differ-. EPJ Web of Conferences ences were observed from sample to sample [4, 5], under several aspects such as bolometric performance, light yield (LY) and the ratio of α’s to β, γ’s LY (i.e. the quenching factor, QF). Preliminary characterization is necessary: in this work we provide a series of useful procedures and parameters, having investigated the optical and structure properties of a crystal which exhibited excellent bolometric performances. We assembled a prototype scintillating bolometer and operated it aboveground in order to assess energy resolution and α/β, γ discrimination capability, we performed optical and X-ray diffraction measurements on the same ZnSe sample
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