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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. 

Double-beta decays of 100Mo from the 6.0195-year exposure of a 6.914 kg high-purity sample were recorded by the NEMO-3 experiment that searched for neutrinoless double-beta decays. These ultrarare transitions to 100Ru have a half-life of approximately 7 × 1018 years and have been used to conduct the first-ever search for periodic variations of this decay mode. The Lomb-Scargle periodogram technique, and its error-weighted extension, were employed to look for periodic modulations of the half-life. Data show no evidence at the 95% confidence level of modulations with amplitude greater than 2.5% in the frequency range of 0.33225 yr−1 to 360 yr−1. 

The SuperNEMO experiment will search for neutrinoless double-beta decay (0νββ), and study the Standard-Model double-beta decay process (2νββ). The SuperNEMO technology can measure the energy of each of the electrons produced in a double-beta (ββ) decay, and can reconstruct the topology of their individual tracks. The study of the double-beta decay spectrum requires very accurate energy calibration to be carried out periodically. The SuperNEMO Demonstrator Module will be calibrated using 42 calibration sources, each consisting of a droplet of 207Bi within a frame assembly. The quality of these sources, which depends upon the entire ^207Bi droplet being contained within the frame, is key for correctly calibrating SuperNEMO's energy response. In this paper, we present a novel method for precisely measuring the exact geometry of the deposition of 207Bi droplets within the frames, using Timepix pixel detectors. We studied 49 different sources and selected 42 high-quality sources with the most central source positioning. 

Double-beta decays of 100Mo from the 6.0195-year exposure of a 6.914 kg high-purity sample were recorded by the NEMO-3 experiment that searched for neutrinoless double-beta decays. These ultra-rare transitions to 100Ru have a half-life of approximately 7  1018 years, and have been used to conduct the rst ever search for periodic variations of this decay mode. The Lomb-Scargle periodogram technique, and its error-weighted extension, were employed to look for periodic modulations of the half-life. Monte Carlo modeling was used to study the modulation sensitivity of the data over a broad range of amplitudes and frequencies. Data show no evidence of modulations with amplitude greater than 2.5% in the frequency range of 0:33225 y􀀀1 to 365:25 y􀀀1. 

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.