The effect of current profile evolution on plasma-limiter interaction and the energy confinement time

PLT experiments are described which illustrate the importance of controlling the evolution of the discharge. The bearing of current-evolution effects of plasma-limiter interaction and on energy confinement is discussed. It is shown that adjustment of the gas influx makes it possible to decrease plasma-limiter interaction and the influx of high-Z impurities from either stainless-steel or tungsten limiters and also to improve the energy confinement time. It is concluded that techniques aimed at profile control should be developed further and implemented, in order to minimize the high-Z impurity influx and to optimize both the temperature and the confinement-quality parameter of the discharge.