Impurity transport in JET using laser injected impurities in Ohmic and radiofrequency heated plasmas

Abstract

Small quantities of medium-Z and high-Z impurities were injected into JET plasmas and their progression was followed by two soft X-ray cameras with good spatial and temporal resolution. The results show that the transport of impurities is much slower in the central region of the plasma than outside of it and that it is greatly enhanced during sawtooth crashes. Simulation of the evolution of the emissivity profiles using an impurity transport code yielded values for the radially dependent transport coefficients; in particular, these values were compared for cases of ohmically heated plasmas and RF heated plasmas.