Internal contamination of the Cs2HfCl6 crystal scintillator Cardenas, C.; Burger, A.; DiVacri, M.L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2017, Letnik:
872
Journal Article
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The internal contamination (radio-purity) of a cesium hafnium chloride (Cs2HfCl6) crystal scintillator and its starting material (CsCl, HfCl4 initial and after 3-fold static sublimation purification) ...was studied by HR-ICP-MS and with an ultra-low-background high purity germanium (ULB-HPGe) detector deep underground. This study was conducted for the purpose of assessing the feasibility of using CHC as a potential detector to the search for rare α decay occurring in Hafnium isotopes. Despite the low radio-purity of starting material, the resulting analysis concluded that the grown CHC crystal is free of nuclides of the U/Th natural decay chain. Only a limit was set on their activities to a few mBq/kg. However, the crystal was found to contain artificial and cosmogenic radionuclides: 137Cs at 0.8 Bq/kg, 132Cs at 25 mBq/kg, 134Cs at 52 mBq/kg and 181Hf at 14 mBq/kg.
The spectral shape of forbidden beta-decays is a crucial benchmark for nuclear physics calculations and has important implications also for astroparticle physics. Among the interesting isotopes in ...this field, 115In is an excellent candidate, being a primordial nuclide featuring a good compromise among Q-value (497.489(10) keV) and half-life (4.41×1014 yr). In this paper, we propose to exploit a cryogenic calorimeter based on a In2O3 crystal to perform a high-precision measurement of the β-decay energy spectrum, discussing also the results obtained within a preliminary test of this crystal and the next steps to improve the detector performance.
CUORE, an array of 988 TeO
2
bolometers, is about to be one of the most sensitive experiments searching for neutrinoless double-beta decay. Its sensitivity could be further improved by removing the ...background from
α
radioactivity. A few years ago it was pointed out that the signal from
β
s can be tagged by detecting the emitted Cherenkov light, which is not produced by
α
s. In this paper we confirm this possibility. For the first time we measured the Cherenkov light emitted by a CUORE crystal, and found it to be 100 eV at the
Q
-value of the decay. To completely reject the
α
background, we compute that one needs light detectors with baseline noise below 20 eV RMS, a value which is 3–4 times smaller than the average noise of the bolometric light detectors we are using. We point out that an improved light detector technology must be developed to obtain TeO
2
bolometric experiments able to probe the inverted hierarchy of neutrino masses.
Localization and modeling of radioactive contaminations is a challenge that ultra-low background experiments are constantly facing. These are fundamental steps both to extract scientific results and ...to further reduce the background of the detectors. Here we present an innovative technique based on the analysis of
α
-
α
delayed coincidences in
232
Th and
238
U decay chains, developed to investigate the contaminations of the ZnSe crystals in the CUPID-0 experiment. This method allows to disentangle surface and bulk contaminations of the detectors relying on the different probability to tag delayed coincidences as function of the
α
decay position.
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