Impurity transport in T-10 plasmas with ohmic heating

Abstract

Impurity transport in the T-10 tokamak plasma with ohmic heating is studied in this paper. The values of various impurities densities, measured with the use of passive spectral diagnostics in the visible (Zeff), active charge exchange measurements (He, C, O), and integral bolometric measurements with absolute extreme ultraviolet detectors (Fe, W) are shown. The experimental data show that accumulation level is growing with impurity nuclear charge and determined by the parameter , which is common for all sorts of impurities. Accumulation process is determined by neoclassical processes and begins with the increase of impurity content in the plasma and ends with the formation of density profiles more peaked than the ne(r). In discharges with low γ anomalous transport completely dominates. So it prevents the impurity accumulation and flattens their density profiles down to the ne(r). These observations correlates with measured negative (positive) plasma potential in discharges with high γ (low γ). 1D modelling using ASTRA and STRAHL transport codes is performed to describe the behaviour of impurities in a wide range of T-10 ohmic regimes. It is shown that the coefficients of anomalous transport Dan and Van established in Krupin et al (1983 Sov. J. Plasma Phys. 9 529–36) and Krupin et al (1985 12th EPS Conf. on Plasma Physics) by describing the density dynamics of injected argon and potassium ions are applicable for the modelling of the He, C, O, W impurity density profiles and their sources. The analysis of the obtained results allows us to state the existence of a common dependence of the anomalous transport for all ions (impurities and deuterons) on the discharge parameters in the T-10 ohmic regimes.