Role of impurity ions in the impurity influx into the plasma of a fusion device

Experimental data on the fluxes of impurity and hydrogen (deuterium) ions outside the confinement volume of magnetic-confinement fusion devices are analyzed. The sputtering coefficients of a stainless steel surface for sputtering by deuterium ions and also by ions of light impurities (C) and metal impurities are calculated as a function of the electron temperature of the plasma near the wall. The potential difference near the wall is taken into account. It is concluded from a comparison of the relative magnitudes of the fluxes and the sputtering coefficients that the sputtering caused by multiply charged impurity ions plays a leading role in the impurity flux in existing fusion devices