Radial penetration and toroidal spread of laser blow-off aluminum beam in TEXTOR

Limiters and walls are the sources of contamination in tokamak discharges. Impurities released from these surfaces enter the plasma and are ionized. The impurity ions are trapped on a field line, further ionized, and heated and dispersed along the field line. An understanding of this heating and dispersal is required to explain the transport of impurities and, thus, the impurity content of the plasma core. Here the toroidal dispersal of laser blow-off injected aluminum is studied. The spatial distribution of Al I, Al II, and Al III line radiation is measured as a function of time. The measured toroidal distribution of the aluminum ions is compared with the distribution calculated by a one-dimensional transport simulation based on the kinetic theory, and a satisfactory agreement is found showing that the toroidal spread is determined only by Coulomb collisions