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[en] A new preparation of a ²²Na positron source is described. The source is entirely of glass, shock-proff enough for usual purposes and easy to handle. These advantages are combined with high ²²Na diffusion yields and low source corrections. (orig.)

[en] The radionuclide ²²Na is a potential astronomical observable that is expected to be produced in classical novae in quantities that depend on the thermonuclear rate of the ²²Na(p,γ)²³Mg reaction. We have measured the strengths of low-energy ²²Na(p,γ)²³Mg resonances directly and absolutely using a radioactive ²²Na target. We find the strengths of resonances at E_p=213, 288, 454, and 610 keV to be higher than previous measurements by factors of 2.4-3.2, and we exclude important contributions to the rate from proposed resonances at E_p=198, 209, and 232 keV. The ²²Na abundances expected in the ejecta of classical novae are reduced by a factor of ≅2.

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[en] A simple method is described for determining the neutron absorption cross sections for radionuclides produced and consumed in a reactor-neutron flux. Data were obtained for ²²Na which, through application of Westcott's procedure, yielded the following: sigma₀ = 51.1 +- 3.1 Kbarns, s₀ = 2.3 +- 0.1, and Σ' = 100 +- 10 Kbarns

[en] Synoptical conditions of the origin of the cosmogenic ⁷Be and ²²Na extremal concentrations in the surface air of Vilnus were investigated. The increased ⁷Be concentrations resulted from high-altitude valley formation in the western direction from the sampling point for 60% of all the cases and 74% of thases were related to the wind velocities exceeding 30 m/s at a height of 300 mb. The analysis of synoptical conditions in the surface layer has shown that the concentration increase occurred most often in the rear of a cyclone or at the eastern circumference of an anticyclone (30 per cent of the cases) and in the central part of an anticyclone (21 per cent of the cases)

[en] In this study, a gamma-gamma coincidence spectrometry was developed and examined for environmental low-level cosmogenic ²²Na monitoring purposes. The spectrometry consists of two bismuth germanate scintillators (BGO) and XIA LLC Digital Gamma Finder (DGF)/Pixie-4 software and card package. The developed spectrometry was optimized according to the considerations of output count rate and gamma peak energy resolution. This spectrometry provides a more sensitive and effective way to quantify even trace amounts of ²²Na with critical detection limit of 9 mBq. A sophisticated computer simulation was also created with the goal of obtaining a better understanding of the experimental results and gamma-gamma coincidence efficiencies at different sample geometries. (author)

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[en] A new positron accumulation scheme compatible with ultrahigh vacuum conditions has been developed, which is realized by preparing a high density electron plasma as high as ≅10¹¹ cm^-3 and an ion cloud as energy absorbers. The present accumulation rate normalized by the intensity of Na²² positron source is (3.6±0.3)x10²e⁺/s/mCi, which is more than one and a half orders of magnitude higher than other ultrahigh vacuum compatible schemes so far reported