No abstract available

No abstract available

[en] A low-background spectrometer with a germanium-lithium detector designed for developing investigation methods of binary beta-decay of ⁷⁶Ge as well as for measuring material radioactive contamination used in low-background devices is described. Descriptions of passive and active protection of the detector and structure spectrometer diagram are given. Average intensity of the background in the intervals from (400 to 1500 and 2000 to 2100 keV is (2.9±0.4)x10^-2 and (1.8±0.03)x10^-2 count/(h x keV) correspondingly

No abstract available

[en] A description is given of a control block, digital frequency discriminator of anticoincidence signals, timer, dead-time measuring device, spectrometer stabilization system signalization elaborated in order to provide more reliable, stable and simple operation of the low-background installation for investigation into double beta-decay

[en] The results of search of the ⁹⁶Zr neutrinoless double β-decay are described. The ⁹⁶Mo experimental plant is described earlier. The experiment techniqUe is based on measurement of scintillation detector back-ground made of 14 separate plates-scintillators on a polystyrene base in which a defenite nuclei number of the ⁹⁶Zr under study is introduced. The ⁹⁶Zr, ⁹⁶Nb and ⁹⁶Mo levels scheme, background spectra obtained in the course of the experiment are presented. No peculiarities which can be related to possible neutrinoless decay are present in the spectra. Therefore on the basis of experimental data it is possible to estimate only the lower limit of the ⁹⁶Zr half-life period. It has been found that the lower limit of the half-life period with the 68% confidence level probability equals 3x10¹-- ⁹ years. The previously obtained limiting value of the ⁹⁶Zr half-life period equals Tsub(1/2)>=5x10¹⁷ years. It is noted that the obtained in the course of the experiment results do not exceed yet maximum theoretical estimation because of the lack of precise theoretical calculations of the ⁹⁶Zr neutrinoless 2β decay (the data available assume the interval of 10¹³-10²¹ years)

[en] The study is aimed at searching for neutron-free 2β-decay of ¹⁰⁰Mo→¹⁰⁰Ru, the expected decay energy is 3032+-8.6 keV. The ¹⁰⁰Mo, ¹⁰⁰Tc and ¹⁰⁰Ru energy level pattern is given. The general vieW of a neW detecting system located in a working volume of a low-noise installation is shown schematically. The experiment on searching for ¹⁰⁰Mo neutron-free 2β-decay includes measurements of detector noise and possible ¹⁰⁰Mo activity during 2220h. The conclusion is made that in the case of neutron-free 2β-decay the ¹⁰⁰Mo half-life exceeds 1.6x10²¹ years with the 90% confidential probability. The restriction on the electron antineutrino majorana mass of Msub(ν tilde e)<=25 eV is determined. It is evidently understated since consideration of nucleon-nucleon interactions in the particle-particle and particle-hole channel will most likely lead to suppression of a nuclear matrix element. The realistic estimation of the neutrino mass limit is at the 70-100 eV level

[en] A direct experiment is described, carried out in order to search for the neutrinoless 2β decay of ¹³⁰Te. The description of experimental facility is given. As a sample ¹³⁰Te with enrichment up to 92.9% has been used. Three series of measurements are performed: measurement of the pure detector background without a sample (200 hrs), measurement of detector background with a sample of ¹³⁰Te(2300 hrs), remeasurement of a detector background (800 hrs). The background spectra obtained are presented. A limit is established for the dacay half-period, equal to 1.2x10²¹ ys at the confidence probability of 68%. The parameter characterizing the lepton charge nonconservation, corresponding to this limit, is calculated basing on the two-nucleon model and amounts to (3-5)x10^-4

[en] A low-background spectrometric device designed to study double beta decay is described. In order to eliminate effectively the background caused by cosmic radiation and natural radioactivity of the environment, the basic semiconductor or scintillation detector of the system is protected by a 8-cm layer of high-purity mercury stored in a titanium tank. In addition to that the detector and the mercury protection system are surrounded on all sides by 6 plastic scintillators which are scanned by 16 photomultipliers. The basic detector is initiated in anticoincidences with the scintillation protection. A brief characteristic of device electronic units is presented. Results of computations of the detector background index at energies ranging from 50 to 8800 keV are given and corresponding background suppress1on coefficients are listed. It is shown that at an achieved background index it is possible to ascertain for certain nuclei the lifetime limit with respect to the non-neutrino double beta decay at the level of 3x10²¹ years

[en] A direct recognitional experiment aimed at searching for the ¹³⁰Te neutrinoless 2β-decay is described. The flowsheet of the device used in the experiments is presented. It has been described by the authors before and modernized to reduce the background. The experiment included three series of measurements. At first the detector pure background without a sample has been measured (during 200 h), then the detector background with ¹³⁰Te (2300 h) and in conclusion, the background of the detector alone (800 h). To test the statistical confidence of the results the data have been output from the analyzer with the help of a puncher and a digital printer, twice a day. The ¹³⁰Te half-life limit Tsub(1/2) >= 1.2x10²¹ years at the 68% level of confidental probability has been found. A branching ratio corresponding to this limit, i.e. the ratio between the rate of the neutrinoless decay and the rate of the 2β-decay, has been found Rsub(ex)<0.83