Trace impurity transport in doublet III beam heated plasma: Comparison of numerical simulations with decay time of titanium line emission in L- and H-mode discharges

Abstract

Decay time τd of the line emissivity of Ti XX(259.3 Å) injected by a laser blow-off technique has a dependence on the electron density from the L-mode discharges to the H-mode discharges. Time behaviours of titanium line emissions are simulated with a numerical code using a density-dependent, anomalous diffusion coefficient DA and a neoclassical flow velocity in the impurity flux density. The DA of (4−5) ×1019/nc(m2/s) (the local electron density nc is in m−3) can well explain the density dependence of the experimental decay time.