Searching for the β+EC and EC/EC Decays of 74Se Rukhadze, N. I.; Barabash, A. S.; Brudanin, V. B. ...
Bulletin of the Russian Academy of Sciences. Physics,
08/2020, Letnik:
84, Številka:
8
Journal Article
Recenzirano
Double beta decay (β
+
EC, EC/EC) of
74
Se was investigated at the Modane underground laboratory (LSM, France; 4800 m of water equivalent) using the OBELIX ultralow-background HPGe detector with a ...sensitive volume of 600 cm
3
and a sample of natural selenium with a mass of 1.6 kg containing ~0.89% (~14.24 g) of
74
Se. The new experimental limits for β
+
EC and EC/EC decays of
74
Se to ground 0
+
and excited
596 keV, and
1204 keV states of
74
Ge, were obtained from experimental data accumulated over 135 days.
The double beta decay ( beta beta ) is very challenging subject of today's physics. It can be used as a powerful tool to test neutrino properties (e.g. Dirac or Majorana type of neutrino) and lepton ...number conservation. However, these experiments demand very high sensitivity and very strong background reduction. We have been performing intensive R&D towards the use of pixel detector Timepix in the beta beta decay experiments. The Timepix device, operated in Time Over Threshold (TOT) mode, provides spectroscopic capabilities in each individual pixel. The main advantage of such detector is its ability to identify and reject background signals (e.g. tracks made by electrons, alpha particles, muons). It would efficiently recognize the signal of beta beta decay processes. Two pixel detectors, Si (pixel size 55 x 55 mu m super(2)) and CdTe (pixel size 110 x 110 mu m super(2)), were tested in the surface laboratory as well as in the underground laboratories, from the point of view of intrinsic background and the results are presented. Low background materials for construction of the setup were also identified. The first prototype of Silicon Pixel Telescope (SPT) has been tested and future improvements are also presented.
Investigating the Double Beta Decay of 58Ni Rukhadze, N. I.; Brudanin, V. B.; Klimenko, A. A. ...
Bulletin of the Russian Academy of Sciences. Physics,
06/2018, Letnik:
82, Številka:
6
Journal Article
Recenzirano
Double beta decay (β +
EC
,
EC/EC
) of
58
Ni is investigated at France’s Modane Underground Laboratory (4800 m water equivalent) using the OBELIX ultralow-background HPGe detector with a sensitive ...volume of 600 cm
3
and a natural nickel sample of ~68% 58Ni with a mass of ~21.7 kg. After preliminary analysis of the experimental data accumulated over ~144 days, new experimental limits are obtained for the 2νβ
+
EC
decay of
58
Ni to the 0
+
ground state and the 2
1
+
, 811 keV excited state of
58
Fe, and for the 2ν
EC/EC
decay of
58
Ni to the 2
1
+
, 811 keV and 2
2
+
, 1675 keV excited states of
58
Fe. The limits are
T
1/2
(β
+
EC
,0→0
+
) > 1.7 × 10
22
yr,
T
1/2
(β
+
EC
,0→2
1
+
) > 2.3 × 10
22
yr,
T
1/2
(
EC/EC
,0→2
1
+
) > 3.3 × 10
22
yr, and
T
1/2
(
EC/EC
,0→2
2
+
) > 3.4 × 10
22
yr. Experimental limit T
1/2
(0ν
EC/EC
–res, 1918 keV > 4.1 × 10
22
yr is obtained for resonant neutrinoless radiative EC/EC decay with an energy of 1918.3 keV. All limits are at 90% CL.
A new experiment devoted to searches for double electron capture in Cd-106 decay is being performed at the Modane underground laboratory (4800 mwe) with the 32-detector TGV-2 spectrometer. The limit ...T (1/2)(2 nu EC/EC) > 2.0x10(20) yr at a 90%confidence level (C.L.) was obtained from a preliminary analysis of data obtained over 2250 h of measurements with about 23.2 g sample enriched in the isotope Cd-106 to 99.57%. The limits T (1/2)(KL, 2741 keV) > 0.9 x 10(20) yr and T (1/2)(KK, 2718 keV) a parts per thousand << 1.4 x 10(20) yr at a 90% C.L. on the neutrinoless decay of Cd-106 were obtained from measurements performed with the Obelix low-background spectrometer from high-purity germanium (HPGe spectrometer) for a sample of mass about 23.2 g enriched in the isotope Cd-106.
A novel experimental approach to search for double electron capture (EC/EC) is discussed in this article. R&D for a new generation EC/EC spectrometer based on silicon pixel detectors (SPDs) has been ...conducted since 2009 for an upgrade of the TGV experiment. SPDs built on Timepix technology with a spectroscopic readout from each individual pixel are an effective tool to detect the 2 upsilon EC/EC signature of the two low energy X-rays hitting two separate pixels. The ability of SPDs to indentify alpha / beta / gamma particles and localize them precisely leads to effective background discrimination and thus considerable improvement of the signal-to-background ratio (S/B). A multi-SPD system, called a Silicon Pixel Telescope (SPT), is planned based on the experimental approach of the TGV calorimeter which measures thin foils of enriched EC/EC-isotope sandwiched between HPGe detectors working in coincidence mode. The sources of SPD internal background have been identified by measuring SPD radiopurity with a low-background HPGe detector as well as by long-term SPD background runs in the Modane underground laboratory (LSM, France), and results of these studies are presented.
A new experiment devoted to searches for double electron capture in sup.106Cd decay is being performed at the Modane underground laboratory (4800 mwe) with the 32-detector TGV-2 spectrometer. The ...limit T.sub.1/2 (2υEC/EC) > 2.0 x 10.sup.20 yr at a 90% confidence level (C.L.) was obtained from a preliminary analysis of data obtained over 2250 h of measurements with about 23.2 g sample enriched in the isotope sup.106Cd to 99.57%. The limits T.sub.1/2(KL 2741 keV) > 0.9 x 10.sup.20 yr and T.sub.1/2(KK 2718 keV) >> 1.4 x 10.sup.20yr at a 90% C.L. on the neutrinoless decay of sup.106Cd were obtained from measurements performed with the Obelix low-background spectrometer from high-purity germanium (HPGe spectrometer) for a sample of mass about 23.2 g enriched in the isotope sup.106Cd.
A new multi-detector spectrometer based on Timepix silicon pixel detectors is developed to investigate the 2ν
EC
/
EC
decay of
106
Cd. The detectors have high efficiency for recording two low-energy ...KX radiation quanta emitted during 2ν
EC
/
EC
decay. The ability of pixel detector to identify α, β, and γ particles and precisely localize them allows us to suppress background radiation efficiently. Test measurements for an assembly of two pixel detectors in an underground laboratory were performed. They showed the possibility of using them in the search for the 2ν
EC
/
EC
decay of
106
Cd.
The main limitation in the high-sensitive HPGe gamma-ray spectrometry has been the detector background, even for detectors placed deep underground. Environmental radionuclides such as 40K and decay ...products in the 238U and 232Th chains have been identified as the most important radioactive contaminants of construction parts of HPGe gamma-ray spectrometers. Monte Carlo simulations have shown that the massive inner and outer lead shields have been the main contributors to the HPGe-detector background, followed by aluminum cryostat, copper cold finger, detector holder and the lead ring with FET. The Monte Carlo simulated cosmic-ray background gamma-ray spectrum has been by about three orders of magnitude lower than the experimental spectrum measured in the Modane underground laboratory (4800 m w.e.), underlying the importance of using radiopure materials for the construction of ultra-low-level HPGe gamma-ray spectrometers.
•Monte Carlo simulations of HPGe gamma-ray spectrometer background for Modane underground laboratory was carried out.•The GEANT4 software package was applied in simulations of background gamma-ray spectra.•The spectrometer background was mainly due to radioactive contamination of its construction parts.•Monte Carlo simulated background was by about three orders of magnitude lower than the experimental one.
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