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

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.