A study of gamma-ray and neutron radiation in the interaction of a 2 MeV proton beam with various materials.
Epithermal neutron source based on a tandem accelerator with vacuum insulation and lithium target has been proposed, developed and operated in Budker Institute of Nuclear Physics. The source is regarded as a prototype of a future compact device suitable for carrying out BNCT in oncology centers. In this work the measurements of gamma-ray and neutron radiation are presented for the interaction of a 2 MeV proton beam with various materials (Li, C, F, Al, V, Ti, Cu, Mo, stainless steel, and Ta). The obtained results enabled the optimization of the neutron-generating target and the high energy beam transportation path.
Qualification of Boron Carbide Ceramics for Use in ITER Ports
Boron carbide has been proposed for the neutron protection of equipment in the ITER diagnostic ports and for reducing the dose to maintenance personnel. The chemical composition, vacuum, and thermal properties of ceramics of boron carbide were studied. It is demonstrated that the outgassing rate of ceramics meets the requirements of the ITER Vacuum Handbook. Calculation of the total gas emission from the ITER equatorial port #11 is carried out. The contact thermal conductivity at the boundary between ceramics and bronze is measured. Manganese content is determined by the method of activation analysis in ceramics. It is shown that sintered and hot-pressed boron carbide ceramics can be used in the ITER diagnostic ports.
Control of the homopause level
Abstract This paper reviews the hypothesis that internal gravity wave breaking in the factor responsible for upper atmosphere turbulence generation and control of the number density at the homopause level. Available data from Mars and Earth support the hypothesis, originally introduced by Lindzen, that breaking thermal tides are responsible for the necessary turbulence. The lowest-order, equatorially trapped, westward-propagating diurnal tidal mode is the primary cause on the Earth, and lower-order westward-propagating semidiurnal modes are the primary cause on Mars. The frequencies and vertical wavenumbers of the responsible modes determine the eddy diffusion coefficients; energy density is only indirectly involved by determining which modes can break. A general scale relationship between tidal heating and velocity amplitude can be used to assess the breaking potential of tidal modes, and is used here as the basis for arguing that the number density at the Martian homopause is likely to have been stable over much of geologic time. Difficulties with this approach arise in the cases of Venus and Titan because of their peculiar zonal winds. For Jupiter and Saturn, internal gravity waves generated by nontidal mechanisms probably control the homopause.