[en] Neutron concentration and neutron output from twolayer loading target during deuteron beam braking in first layer of target is studied theoretically. Struggling effect on neutron output is discussed

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[en] The problem on the capture rate of thermalized positrons by spherical defects in an infinite elasto-anisotropic cubic crystal is considered. Defects in such a crystal attract a complementary diffusive flux of positrons. The calculation has been performed in the assumption that the elastic anisotropy of a crystal and the anisotropy of the positron diffusion coefficient D are small, and the anisotropy of surface energy is negligibly small. It has been assumed that the diffusive and elasto-diffusive fluxes are paralled with the positron density gradient and with the elastic tension gradient respectively. An expression for the positron capture rate is obtained. The term, allowing for the elasto-diffusive interaction of positrons and defects, may change its sign according to the ratio of external pressure, gas pressure in a defect, Laplace pressure and the sign of the metal anisotropy parameter, i.e., under certain ratios the elasto-diffusive interaction of positrons with defects may favour or inhibit positron capture

[en] A problem is clarified, whether positron interaction with crystalline defects is limited only by the following annihilation. Interpreted is the nature of lattice instability (LI), formed during positron capture by instable, short-lived Frenkel defects. Life time of vacancies constitutes approximately 10^-12 s and it does not depend on temperature. In a wide temperature range (from 200 to 2000 K) presented is temperature dependence of the annihilation parameter, which shows, that the lower is the energy of vacancy formation, the higher is LI in the region of heat vacancies. In the before-vacancy region LI is determined by an annihilation angular parameter. It is shown, that local character of positron interaction with the lattice, high sensitivity to atomic environment make them good sounds, initiating and informing about its level

[en] Positron annihilation, employed to study the radiation effect of a hard gamma-radiation upon single crystals of molybdenum, has indicated that during the annealing of defects caused in a single crystal of molybdenum by irradiation with high-energy gamma-photons, the annihilation parameter undergoes nonmonotonic decrease. The consideration of defects in single crystal leads to the conclusion that their parameters prior to annealing correspond to small-diameter pores having a positron capture effectiveness much greater than that of the vacancies. Discussed is the possible mechanism of formation of defects in gamma-irradiation

[en] 30 MeV proton radiation was studied for its effect on the eletAron-positron annihilation (EPA) parameters in Cr-Ru alloys. A relatively small doping of Cr with Ru is shown to change essentially the EPA parameters. There are concentration ranges where the EPA-parameter variations upon the irradiation are practically stabilized

[en] Angular distributions of annihilation photons from hard 50 MeV gamma radiation in tugsten single crystal alloys doped with rhenium are investigated in the paper. Samples of W-Re alloys were prepared by electron-beam crucibleless zone melting and subsequently heat treated at 1650 deg C under vacuum conditions (10^-7 torr). The samples were exposed to betatron hard 50 MeV gamma irradiation to integrated doses of approximately 3x10⁶ Roe. For the annealed and the irradiated samples spectral distribution curves were approximated by one parabola and one Gaussian curve. The annealed samples practically have no parabolic component found for the annealed samples. This is due to radiation-induced vacancies forming a complex with impurity Re atoms. Comparison of results obtained for rhenium-doped alloys (1.5, 3.5, 4.5% Re) allows one to conclude that the W-3.5%Re alloy is more stable as compared with the other alloys

[en] The radiation-induced defects in cobalt irradiated by slowing-down radiation beam from betatron having maximal γ-quantum energy of 50 MeV and approximately 3x10⁶ R dose were studied by the positron annihilation method. Vacancy-type defects are found to be the trapping centres for positrons in irradiated cobalt

[en] Positron interaction with radiation defects in polycrystalline niobium after γ-irradiation at room temperature with an integral dose up to 3x10⁶ r, is investigated using the method of positron annihilation. The curves of the angular distribution of annihilation photons have been obtained after various annealing stages in the 50-900 deg temperature range. It is shown that niobium irradiation with hard γ-rays leads to the formation of vacancy defects, stable up to 400 deg C due to bonds with impurity atoms. Centres of positron capture are formed at 600-900 deg C which are supposed to be connected with nitride and oxide particles

[en] An experimental generator of fast neutrons via T(d,n)⁴He reaction is described. Neutron yield of 5.10¹¹ neutron·s^-1 is achieved. (author)