Transport Modeling of ECH (Electron-Cyclotron Heating) and Neutral-Beam-Heated Plasmas in the Advanced Toroidal Facility.

摘要

The report reviews the transport modeling of ECH heating and NBI heating in the ATF torsatron. Approximately steady-state plasmas are obtained with 200 kW of second harmonic ECH in ATF. Measured Thomson scattering T/sub e/ profiles, spectroscopic T/sub i/ values, stored energy, and spectroscopic emission levels may be reproduced with the predictive transport code PROCTR using a multi-pass ECH model and assuming neoclassical heat transport for both electrons (xie) and ions (xii). In addition, xie must be enhanced in the outer half of the plasma (in the region /tau/ > /1/2/) to reproduce the narrow observed T/sub e/ profile shape. This enhancement is partially attributed to field errors, the cause of which has been identified and corrected. NBI heated discharges exhibit dynamic behavior and do not reach steady-state in ATF experiments. During NBI heating with 600 kW of co-injection, the density ramps up nearly linearly from the value obtained in the ECH phase of the discharge. At the same time, the stored energy and driven toroidal plasma current rise to a peak and then all to a low value. Near the end of the stored-energy decrease, the plasma temperature is observed to collapse suddenly in the presence of the full heating power. At the time of collapse, the electron density shows a discontinuous change in slope from an upward ramp to a slow decrease and the spectroscopic emission from intermediate charge states of light impurities disappears. (ERA citation 14:029897)