The effect of EC heating on impurity transport in T-10

To analyze the effect of EC heating on impurity transport a short argon gas- puff (t~15-20 ms) was applied in a stationary phase of both OH and ECH discharges. The argon density profile evolution after puffing was studied by measurements of the He- and H-like argon ion s line radiation. The registration of radiation of 2p ‐ 1s Ar +16 and Ar +17 lines was carried out by means of the X-ray crystal monochromator RM-2 with multiwire gas chamber which enables to register 48 chords with time resolution of 10 µs. The measurements were m ade for both argon lines emission and recombination continuum radiation in a series cons isting of reproducible discharges by means of wavelength change in the cryst al monochromator from pulse to pulse. Two types of ohmic heating discharges and corresponding to them two types of ECH discharges, characterized by different EC power space deposition, are compared. Workin g parameters are as follows: the plasma current I p = 250 kA, the central line averaged density ne = 2.5◊10 19 m ‐3 and the EC power 0.75 - 1 MW in the case of the centrally deposited ECH; Ip = 180 kA, ne = 1.5◊10 19 m ‐3 , the EC power of 650 MW for off-axis EC heating placed at ~0.4. Sawtooth activity was suppressed in the regimes with off-axis EC heat ing, in other discharges of this series, sawteeth were presented. Argon gas-p uff has been performed in all four types of OH and EC regimes for transport study. The argon density evo lution at the transition from OH to ECH regime was analyzed as well. For impurity transport simulations two impurity transport codes, T -10 impurity code [2] and STRAHL code have been used. The main plasma simulations were carried out by means of ASTRA code [3]. Impurity transport analysis is based on solution s of the radial transport equations together with ionization balance for all ionization stages of argon