Plasma Wall Interactions in Heated Plasmas

Abstract

With the development of larger, more powerful magnetic confinement devices, the study of plasma-wall interactions becomes increasingly relevant to the controlled thermonuclear fusion program. To increase the plasma temperature in Tokamaks from the value reached by ohmic heating (1 – 2 keV), toward the value necessary for self sustaining fusion reactions (5 – 10 keV) requires a tremendous amount of additional power. This is achieved either by the injection of high energy neutral particles — called neutral beam injection (NBI) - or by high frequency electromagnetic radiation — also called radiofrequency heating (RF). In recent experiments the amount of power introduced by these “additional heating” schemes, greatly exceeds the ohmic power (in JET, PNBI + PRF = 25 MW, POH = 2 MW). While substantially increasing the energy density of the plasma a new set of problems are introduced which are associated with the increased plasma wall interactions due to additional heating.