Simulation of Improved Confinement Dischanges and Sawtooth Period with ECH and Current Drive in TCV
The PRETOR 1-1/2 D transport code has been modified to simulate discharges with the highly flexible electron cyclotron heating (ECH) system of the TCV tokamak. The code has been interfaced with the TORAY ray-tracing code, used to determine the power deposition profile in TCV on a regular basis. Past experiments with intense ECH clearly pointed out the effects of the power deposition profile and the current drive on the electron energy confinement and on the sawtooth activity. Discharges with Improved Central Confinement have been produced using particular heating and current drive schemes. Transport simulations, with transport coefficients based on the RLW transport model and a sawtooth crash model based on a critical shear value at q=1, already validated for ohmic discharges in TCV, and are in surprisingly good agreement with the experimental results. For discharges with intense central counter current drive, and Improved Central Confinement, the simulation results predict an extreme sensitivity to very small changes in the location of the current drive, (i.e. within the expected error bars). This sensitivity has been confirmed by preliminary experimental results. Due to this strong sensitivity, the simulation results do not allow a conclusive validation of the transport model. Some numerical results agree well with experiments even when the confinement time exceeds the RLW global scaling law by a factor of 3.5. With very localized ECH power deposition profiles, the experimental sawtooth period strongly depends on the power deposition localization and on even very small amounts of current drive.
Bibliographic Reference: An article published in: Theory of Fusion Plasmas (2000), pp.73-86
Record Number: 200013670 / Last updated on: 2001-09-18
Original language: en
Available languages: en