Semi-empirical method of calculation of quenching factors for scintillators is described. It is based on classical Birks formula with the total stopping powers for electrons and ions which are ...calculated with the ESTAR and SRIM codes, respectively. Method has only one fitting parameter (the Birks factor
kB) which can have different values for the same material in different conditions of measurements and data treatment. A hypothesis is used that, once the
kB value is obtained by fitting data for particles of one kind and in some energy region (e.g. for a few MeV
α
particles from internal contamination of a detector), it can be applied to calculate quenching factors for particles of another kind and for another energies (e.g. for low energy nuclear recoils) if all data are measured in the same experimental conditions and are treated in the same way. Applicability of the method is demonstrated on many examples including materials with different mechanisms of scintillation: organic scintillators (solid
C
8
H
8
, and liquid
C
16
H
18
,
C
9
H
12
); crystal scintillators (pure
CdWO
4
,
PbWO
4
,
ZnWO
4
,
CaWO
4
,
CeF
3
, and doped
CaF
2
(Eu), CsI(Tl), CsI(Na), NaI(Tl)); liquid noble gases (LXe). Estimations of quenching factors for nuclear recoils are also given for some scintillators where experimental data are absent (
CdWO
4
,
PbWO
4
,
CeF
3
,
Bi
4
Ge
3
O
12
, LiF, ZnSe).
We report the measurement of the two-neutrino double-beta ($2\nu\beta\beta$) decay of $^{100}$Mo to the ground state of $^{100}$Ru using lithium molybdate (\crystal) scintillating bolometers. The ...detectors were developed for the CUPID-Mo program and operated at the EDELWEISS-III low background facility in the Modane underground laboratory. From a total exposure of $42.235$ kg$\times$d, the half-life of $^{100}$Mo is determined to be $T_{1/2}^{2\nu}=7.12^{+0.18}_{-0.14}\,\mathrm{(stat.)}\pm0.10\,\mathrm{(syst.)}\times10^{18}$ years. This is the most accurate determination of the $2\nu\beta\beta$ half-life of $^{100}$Mo to date. We also confirm, with the statistical significance of $>3\sigma$, that the single-state dominance model of the $2\nu\beta\beta$ decay of $^{100}$Mo is favored over the high-state dominance model.
The search for neutrinoless double β decay probes lepton number conservation with high sensitivity and investigates the neutrino nature and mass scale. Experiments presently in preparation will cover ...the quasi-degeneracy region of the neutrino mass pattern. Probing the inverted hierarchy region requires improved sensitivities and next-generation experiments, based either on large expansions of the present searches or on new ideas. We examine here a novel technology relying on ZnMoO4 scintillating bolometers, which can provide an experiment with background close to zero in the ton × year exposure scale. The promising performance of a pilot detector is presented, both in terms of energy resolution and background control. A preliminary study of the sensitivities of future experiments shows that the inverted hierarchy region is within the reach of the technique here proposed. A realistic phased approach program towards a next-generation search is presented and briefly discussed.
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 406–655nm. Samples of ZnMoO4 crystals with masses of 5.07g and 23.8g were operated as scintillating bolometers at temperatures below 30mK, 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.
Radioactive contamination of SrI2(Eu) crystal scintillator Belli, P.; Bernabei, R.; Cerulli, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2012, Letnik:
670
Journal Article
Recenzirano
Odprti dostop
A strontium iodide crystal doped by europium (SrI2(Eu)) was produced by using the Stockbarger growth technique. The crystal was subjected to a characterization that includes relative photoelectron ...output and energy resolution for γ quanta. The intrinsic radioactivity of the SrI2(Eu) crystal scintillator was tested both by using it as scintillator at sea level and by ultra-low background HPGe γ spectrometry deep underground. The response of the SrI2(Eu) detector to α particles (α/β ratio and pulse shape) was estimated by analysing the 226Ra internal trace contamination of the crystal. We have measured: α/β=0.55 at Eα=7.7MeV, and no difference in the time decay of the scintillation pulses induced by α particles and γ quanta. The application of the obtained results in the search for the double electron capture and electron capture with positron emission in 84Sr has been investigated at a level of sensitivity: T1/2∼1015–1016yr. The results of these studies demonstrate the potentiality of this material for a variety of scintillation applications, including low-level counting experiments.
The resonance excitation of the 7Li nuclei in a LiF crystal with mass of 553 g by hypothetical axions emitted in the deexcitation of the 7Li nuclei in the Sun was searched for deep underground at the ...Gran Sasso National Laboratories (LNGS) of INFN (3600 m w.e.). The data collected with a low background HP Ge detector 244 cm3 during 4044h have allowed us to set the limit on the axion mass: ma<8.6 keV (90% C.L.) which is the best one for the 7Li solar axions to-date.
Random coincidences of nuclear events can be one of the main background sources in low-temperature calorimetric experiments looking for neutrinoless double-beta decay, especially in those searches ...based on scintillating bolometers embedding the promising double-beta candidate Formula omitted Mo, because of the relatively short half-life of the two-neutrino double-beta decay of this nucleus. We show in this work that randomly coinciding events of the two-neutrino double-beta decay of Formula omitted Mo in enriched Li Formula omitted detectors can be effectively discriminated by pulse-shape analysis in the light channel if the scintillating bolometer is provided with a Neganov-Luke light detector, which can improve the signal-to-noise ratio by a large factor, assumed here at the level of Formula omitted on the basis of preliminary experimental results obtained with these devices. The achieved pile-up rejection efficiency results in a very low contribution, of the order of Formula omitted counts/(keV Formula omittedkg Formula omittedy), to the background counting rate in the region of interest for a large volume ( Formula omitted cm Formula omitted) Li Formula omitted detector. This background level is very encouraging in view of a possible use of the Li Formula omitted solution for a bolometric tonne-scale next-generation experiment as that proposed in the CUPID project.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).Random coincidence of events (particularly from two neutrino double beta decay) could be one of the main sources of ...background in the search for neutrinoless double beta decay with cryogenic bolometers due to their poor time resolution. Pulse-shape discrimination by using front edge analysis, mean-time and ... methods were applied to discriminate randomly coinciding events in ZnMoO... cryogenic scintillating bolometers. These events can be effectively rejected at the level of 99 % by the analysis of the heat signals with rise-time of about 14 ms and signal-to-noise ratio of 900, and at the level of 92 % by the analysis of the light signals with rise-time of about 3 ms and signal-to-noise ratio of 30, under the requirement to detect 95 % of single events. These rejection efficiencies are compatible with extremely low background levels in the region of interest of neutrinoless double beta decay of ...Mo for enriched ZnMoO... detectors, of the order of ... counts/(y keV kg). Pulse-shape parameters have been chosen on the basis of the performance of a real massive ZnMoO... scintillating bolometer. Importance of the signal-to-noise ratio, correct finding of the signal start and choice of an appropriate sampling frequency are discussed.
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