Yu. L. Igitkhanov

First wall and divertor plate sputtering in a tokamak reactor

Abstract Calculations are presented for the sputtering yields averaged over energy and angular distributions of incident deuterium and tritium ions on various materials proposed for the divertor plates and first wall of a tokamak reactor (C, Al, Ti, Fe, Mo, W). Modifications to the particle energy distribution function due to acceleration in the sheath electric field are included and the calculations are performed over the energy range characteristic of the particles in the plasma boundary. The results are restricted to the case of magnetic field lines normal to the divertor plate surface.

Non-local transport effects on the tokamak SOL plasma parameters

Abstract The effect of non-local transport on the SOL-plasma parameters in a tokamak with a poloidal divertor is considered. A self-consistent model of plasma and neutral gas transport has been developed. The plasma is described by a set of 1D equations for the particle, and parallel momentum and heat transport, taking into account non-local heat fluxes and viscous stresses. The non-local fluxes are determined by a set of equations for higher-order moments, obtained on the basis of the Grad method. The neutral gas behaviour is represented in the diffusion approximation. Calculations have been performed using the PNL1D code for ASDEX-like plasma parameters. A comparison between the longitudinal distribution of plasma parameters in the SOL, calculated using both local and non-local transport models will be presented.

Light impurity radiation from the ITER divertor plasma

Abstract The possible use of low Z materials for the ITER divertor plates is discussed. A non coronal radiation model has been developed which indicates that strong enhancement in the radiated power from the divertor may take place when finite confinement is considered. For carbon this leads to stable operating regimes at low electron temperature. It is shown that relaxation oscillations in the dynamical behaviour of impurity density and electron temperature are possible, and can lead to a large decrease in the gross erosion rate of the divertor plates both for carbon and beryllium.

A review of edge physics issues for ITER

Abstract The importance of edge plasma physics in connection with the ITER design study of reactor plasmas has recently been widely recognised. Our understanding of the processes taking place in the tokamak boundary region is far from satisfactory at present. Nevertheless, certain progress has been made and the key issues are reviewed in this paper. They are: the interdependence of plasma parameters at the edge and core regions, the properties of plasma transport in the SOL, helium and other impurity transport properties in the edge and the possibility of active control of the power exhaust channels. Finally, the development and validity of numerical models of the plasma edge are discussed.

Effect of a temperature gradient on the neutral-atom distribution in the boundary region of the plasma column

A plasma temperature gradient leads, on the one hand, to additional localization of neutrals in the region near the wall, and, on the other, to a non-exponential (power) law governing the decrease in the atom density near the wall. It is shown that under conditions of inverse temperature gradient at the edge of the column the neutral flow from the chamber walls is intensified.

A possibility of wall-protecting cold-plasma layer formation in a tokamak reactor

It is shown that, on the assumption of neoclassical transport processes, a stationary regime of thermonuclear reactions in a thermonuclear reactor is possible, in which case, in the region close to the wall, a protective layer of dense, cold plasma capable of protecting the wall from sputtering is formed.