PARTICLE FUELING IN TORE SUPRA

Particle control is an essential requirement for long-pulse operation. Besides steady-state particle exhaust, the complementary key element is particle fueling. Three fueling methods are currently used in Tore Supra: conventional gas puffing, supersonic molecular beam injection, and pellet injection. In addition to a technical description of the corresponding systems, this paper presents an overview of different studies characterizing these methods in terms of fueling efficiency and ability to fuel long discharges or to obtain high-density plasmas with no confinement degradation. An analysis of the interaction between the plasma and the pellet or supersonic beam is also given, including the physics of the homogenization of the deposited particles in the background plasma (importance of the edge cooling and of the del B-induced displacement) or the transport-induced modification for deep-matter penetration (triggering of an improved confinement phase or, conversely, of a sawtooth crash when a pellet crosses the q = 1 surface).