Reduction of Plasma Heat Flow by Sheath‐Presheath Modifications with Ponderomotive Force

Abstract

A r. f. induced directed force exerted by the application of r. f. voltage on the divenor plate or by introducing r. f. electric field in front of the plate is taken into account for the analysis on sheath-presheath formation in a very simple manner. The ponderomotive force repels electrons coming to the divertor plate, which results in a reduction of the electron heat flow. The reduction of ionic impact energy to the plate is also expected even for presheath ,modification combined with positive divertor biasing as well as for successful sheath modification.

Parallel heat flux limits in the tokamak scrape-off layer

“…Much of the work originates, and is intimately connected, with the problem of the electrostatic sheath at the plasma-solid interface; an excellent discussion of the sheath problem may be found in [26,86,122,124]. Within this area, much effort has been devoted to calculating, both analytically and numerically, the energy transmission properties of the sheath, and formulating boundary conditions for the pre-sheath (SOL) moment equations in terms of the heat transmission coefficients [16,29,30,54,65,66,68,87,92,94,103,106,108,110,116,127]. Two numerical techniques are typically employed in solving the Fokker-Planck equation in the SOL: finite difference discretization in two (1D1V) to five (2D3V) dimensions (1D2V being typical), which leads to the Table 1.…”