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A radiochemical method for producing 82Se sources with an ultra-low level of contamination of natural radionuclides (40K, decay products of 232Th and 238U) has been developed based on cation-exchange chromatographic purification with reverse removal of impurities. It includes chromatographic separation (purification), reduction, conditioning (which includes decantation, centrifugation, washing, grinding, and drying), and 82Se foil production. The conditioning stage, during which highly dispersed elemental selenium is obtained by the reduction of purified selenious acid (H2SeO3) with sulfur dioxide (SO2) represents the crucial step in the preparation of radiopure 82Se samples. The natural selenium (600 g) was first produced in this procedure in order to refine the method. The technique developed was then used to produce 2.5 kg of radiopure enriched selenium (82Se). The produced 82Se samples were wrapped in polyethylene (12 microm thick) and radionuclides present in the sample were analyzed with the BiPo-3 detector. The radiopurity of the plastic materials (chromatographic column material and polypropylene chemical vessels), which were used at all stages, was determined by instrumental neutron activation analysis. The radiopurity of the 82Se foils was checked by measurements with the BiPo-3 spectrometer, which confirmed the high purity of the final product. The measured contamination level for 208Tl was 8–54 microBq/kg, and for 214Bi the detection limit of 600 microBq/kg has been reached.
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Search for the double-beta decay of $^{82}$Se to the excited states of $^{82}$Kr with NEMO-3
The double-beta decay of 82Se to the 0+1excited state of 82Kr has been studied with the NEMO-3 detector using 0.93kg of enriched 82Se measured for 4.75y, corresponding to an exposure of 4.42kg·y. Adedicated analysis to reconstruct the γ-rays has been performed to search for events in the 2e2γchannel. No evidence of a 2νββdecay to the 0+1state has been observed and a limit of T2ν1/2(82Se, 0+gs→0+1) >1.3 ×1021yat 90%CL has been set. Concerning the 0νββdecay to the 0+1state, alimit for this decay has been obtained with T0ν1/2(82Se, 0+gs→0+1) >2.3 ×1022yat 90%CL, independently from the 2νββdecay process. These results are obtained for the first time with a tracko-calo detector, reconstructing every particle in the final state.
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- Award ID(s):
- 1811901
- PAR ID:
- 10308972
- Date Published:
- Journal Name:
- Nuclear physics
- Volume:
- 996
- ISSN:
- 0375-9474
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/doi:10.1016/j.nuclphysa.2020.121701
