V. V. Kuzminov

Precise measurement of 14C beta spectrum by using a wall-less proportional counter

The technique and results of a precise measurement of the 14C beta spectrum in the energy range 10–160 keV by using a wall-less proportional counter are presented. The results of analysis and the inclusion of possible factors that distort the spectrum in the calculation of the detector response function are reported. Considerable deviations from the distribution expected for an allowed transition are found.

Correlation of variations in the thermal neutron flux from the Earth’s crust with the Moon’s phases and with seismic activity

The results of the long-term recording of thermal neutron flux near the Earth’s surface with the use of an unshielded scintillation thermal-neutron detector are presented. The data obtained indicate the presence of periodic variations in the thermal neutron flux with the lunar diurnal and the lunar monthly periods. A hypothesis about the existence in the Earth’s crust of radon-neutron tidal variations in the concentration of thermal neutrons, correlated with the Moon’s phases and which have the gravitational origin, is formulated and confirmed experimentally. A simple mathematical model is proposed, which satisfactorily describes the observed variations. The case of the anomalous behavior of thermal neutrons is presented, which correlates with the high local seismic activity.

Tidal effect in the radon-due neutron flux from the Earth's crust

Baksan Neutrino Observatorys results on variations of thermal neutron flux below and above the ground surface measured with an unshielded scintillator detector are presented. Experimental evidences were obtained of the existence of seasonal wave in the long-term thermal neutron flux variations as well as correlation between this variations and lunar periods.

Monitoring the 222Rn concentration in the air of low-background laboratories by means of an ion-pulse ionization chamber

A brief description of a setup based on a large-size air ion-pulse ionization chamber intended for monitoring the concentration of 222Rn in the air of laboratories is given. The sensitivity of the detector used for performing measurements with an air sample containing radon with a volume activity of 10 Bq m−3 makes it possible to attain 10% statistical accuracy in determining the area of a radon peak in a measurement time of 103 s. The results from long-term measurements of radon concentration in the air of ground-based and underground laboratories are presented.

Ion-pulse ionization chamber for direct measurement of radon concentration in the air

A large-volume (24.8l in total volume, 16.8l in fiducial volume) multiwire pulse ion collection ionization chamber was examined as a detector of α particles from radon decays in the air inside the chamber. The possibility of obtaining spectrometric information from slow ion pulses was tested. An energy resolution of 3.9% for 5.49-MeV α particles was obtained in preliminary measurements. It was shown that a detector of this kind could be used for direct measurements of radon activities in flowing air at a level less than 1 Bq/m3. A radon concentration at a level of 10 Bq/m3 can be measured with an accuracy better than 10 % for a counting time of 103 s. The detector will be used for continuous accurate monitoring of the 222Rn concentration in the air of low-background laboratories.

New limit on the half-life of 78Kr with respect to the 2K(2ν)-capture decay mode

The features of data accumulated for 1817 h in an experimental search for the 2K(2ν)-capture mode of 78Kr decay are discussed. A new limit on the half-life for this decay is found: T1/2≥2.3×1020 yr (at a 90% C.L.).Features of data accumulated at 1817 hours in the experimental search for 2K(2 \nu)-capture decay mode of Kr-78 are discussed. The new limit for this decay half-life is found to be T_{1/2}>2.3 *10^{20} yr. (90% C.L.).

First results of a search for the two-neutrino double-beta decay of 136Xe with high-pressure copper proportional counters

A description of a low-background installation for a new stage of the experimental search for the 2β(2ν) decay of 136Xe with high-pressure copper proportional counters is presented. The first estimate of the decay half-life limit based on the data measured over 4140 h yields T1/2≥2.4×1021 yr (90% C.L.).

Characteristics of a Proportional Counter Filled with CF4 and Additions of Xe

The performance characteristics of a proportional counter filled with a gas mixture of Freon-14 (CF4) and Xe at pressures of 0.8–14.8 atm were measured. Adding some Xe (a 1–2% concentration is optimal) to CF4 was found to approximately halve the operating high voltage needed for achieving the same gas-amplification factor as in pure CF4, improve the energy resolution, and increase the expected ultimate gas-amplification factor by an order of magnitude.

Analysis of α-particle background events in a high-pressure proportional counter

The results of amplitude spectrum measurement and data processing of 222Rn and its daughter nucleus decays in a high-pressure copper proportional counter filled with xenon at a pressure of 14.8a tm are given. The preliminary estimates of the α/e ratio for different E/P values are also presented.