The ECRH/ECCD system on Tore Supra, a major step towards continuous operation

Abstract

The 118 GHz electron cyclotron heating and current drive (ECRH/ECCD) system under development in Cadarache, France, for use on the Tore Supra tokamak (Pain M. et al 1994 Proc. 18th SOFT (Karlsruhe) pp 481-4: Darbos C. et al 2000 Proc. 21st SOFT (Madrid) pp 605-9), is designed to launch 2.4 MW of power for up to 10 min into the plasma. At present two out of six gyrotrons are installed and available for injection of up to 800 kW. This paper concentrates on the generation and transmission of the ECRH/ECCD power for very long pulse operation. The power is injected into the plasma as Gaussian beams by an antenna which, using actively cooled mirrors inside the Tore Supra vacuum vessel, allows extensive control of both the poloidal and toroidal injection angles. The toroidal field on Tore Supra is normally in the range of 3.8-4 T, which for 118 GHz gives almost central deposition at the fundamental electron cyclotron resonance. A pair of actively cooled corrugated mirrors is installed in each matching optics unit at the output of each gyrotron allowing complete control of the polarization of the wave transmitted to the antenna, with the result that pure O-mode-or pure X-mode-power injection can be achieved for all injection angles. In tokamak experiments, a world record energy of 17.8 MJ has been injected into the plasma. New upgraded gyrotrons specified to produce 400 kW for up to 10 min will be introduced over the next 3-4 years.

Demonstration of Effective Control of Fast-Ion-Stabilized Sawteeth by Electron-Cyclotron Current Drive

“…This conclusion is corroborated by the measurement on JET of fast ions with energies of several MeV, again under similar experimental conditions [18]. The effect of co-and counter-ECCD on the sawtooth period has been explored in discharges where the capability of the Tore Supra ECCD system of varying toroidal and poloidal injection angles over a wide range [19] was exploited to sweep the ECCD deposition from outside the q ¼ 1 surface to the plasma center. An overview of one such discharge with co-ECCD is shown in Fig.…”

Synergy of Electron-Cyclotron and Lower-Hybrid Current Drive in Steady-State Plasmas

“…A multiple feedback strategy was employed, with the following actuators: (1) a gas puff to keep the plasma density constant, (2) LH power to keep the plasma current constant, and (3) transformer flux to keep the loop voltage V loop constant and exactly equal to zero. On the stationary phase of this target plasma, EC waves have been injected for a duration of 10 s. Two gyrotrons [16] at 118 GHz have been used to inject a total power P EC 0:7 MW into the plasma in the ordinary mode (1st harmonic), by means of poloidally and toroidally steerable mirrors. During the ECCD phase, the LH power is expected to drop by an amount P LH , because the plasma current is kept constant.…”

Progress in ECRF antenna development for JT-60SA

“…Active cooling for steering mirrors is required for a long pulse and high power ECRF antenna and a front steering antenna/launcher concept with flexible coolant tubes is widely adopted [6][7][8][9]. However, the LM antenna has been proposed to reduce the risk of water leakage in the vacuum vessel due to problems with the flexible coolant tubes, and it has no flexible part for coolant in the vacuum vessel.…”