IMPROVEMENT OF HELIUM IONS BEAM FORMATION AND TRANSPORT SYSTEM

Works on improvement of a beam formation and transport system from an accelerating section output to the target complex on NSC KIPT helium ions linear accelerator with output energy of 4 MeV, used for carrying out of radiating researches are continued. Results of researches spent with electromagnetic quadrupole lenses, forming a triplet are presented. Experiments with injected (120 keV) and accelerated (4 MeV) helium ions beams by means of advanced beam formation and transport system to a target are continued. The proposal on decrease in thermal loading of a triplet is formulated.

EXPERIMENTAL RESEARCH AND WORK DEVELOPMENT ON THE HELIUM IONS LINAC

The paper provides a brief summary of the experimental research carried out at the present time at the materials science complex developed at the NSC KIPT. The main directions for the development of the work carried out have been determined. The complex is based on a linear accelerator of helium ions. The features and advantages of the accelerating structure of the accelerator, which is based on the principle of APF, are described. A technique was de-veloped and irradiation of candidate materials for the divertor and the first wall of the TNR was carried out. The damageability of the irradiated samples could create from 3 to 80 dpa.

Generation of Short-scale Electrostatic Fields in the Solar Atmosphere and the Role of Helium Ions

Theoretical models are presented to show that expansion of plasma in the radial direction from a denser solar surface to a rarefied upper atmosphere with short-scale inhomogeneous field-aligned flows and currents in the form of thin threads itself is an important source of electrostatic instabilities. Multifluid theory shows that the shear flow–driven purely growing electric fields appear in the transition region. On the other hand, plasma kinetic theory predicts that the short-scale current sheets (or filaments) produce current-driven electrostatic ion acoustic (CDEIA) waves in the hydrogen plasma of the transition region that damp out in the system through wave–particle interactions and increase the temperature. Similar processes take place in the solar corona and act positively for increasing the temperature further and maintaining it. The shear flow–driven instabilities and CDEIA waves have short perpendicular wavelengths of the order of 1 m and low frequencies of the order of 1 or several Hz when the ions’ shear flow scale length is considered to be of the order of 1 km. It is pointed out that the purely growing fluid instabilities turn into oscillatory instabilities and the growth rates of kinetic CDEIA wave instabilities are reduced when the dynamics of 10% helium ions is taken into account along with 90% hydrogen ions. Therefore, the role of helium ions should not be ignored in the study of wave dynamics in solar plasma.

Characteristics of Plasma Dynamics in Current Sheets Formed in Helium Plasma

The characteristic features of plasma acceleration in the current sheets are discussed on the basis of an analysis of the structure of electrodynamic forces at successive stages of the evolution of the current sheets formed in the plasma with helium ions. Of particular interest is the generation of reverse currents at the side edges of the sheet and the appearance of forces, which are braking previously accelerated plasma flows.

TRIBOLOGICAL CHARACTERISTICS OF ‘STEEL – CERAMICS-IRRADIATED-BY-HELIUM-IONS’ PAIR

Facility for the tribological characteristics studying of a metal – ceramics pair and parameters of ceramic samples irradiation on the helium ions linear accelerator with energies 0.12 and 4 MeV are resulted. Profiles of damageability and occurrence of target atoms along of helium ions range are calculated for the irradiated TiO2 and Al2O3. Sputtering ratios and dependence of the sputtered atoms quantity on samples thickness are received. Calculations on density change of the irradiated samples are made. Experimental results of a sliding friction factor measurement depending on cycle’s quantity, temperature and irradiation doses are presented. On the basis of microscopic researches and calculation data conclusions are drawn about irradiation influence on interacting pair’s tribological characteristics.