Status of the ECRH system on Tore Supra

An ECRH (Electron Cyclotron Resonance Heating) system capable of delivering 2.4 MW CW is presently under construction at CEA (Commissariat a l'Energie Atomique) Cadarache, for the Tore Supra experiment to provide plasma heating and current drive by Electron Cyclotron Resonance interaction. Due to some limitations observed on the first series tube which achieved 300 kW output power for 110 s, a new study carried out in a collaboration between TED (Thales Electron Devices), the Association Euratom-CEA and the Association Euratom-Confederation Suisse has led to the construction of a new modified gyrotron. The new gyrotron, with a new launcher profile and a better cooling system is now installed in this test bed. A clear improvement in the time required to condition the tube has been observed. On the other hand poor mode purity in the output beam has resulted in the need to implement a cooling system for the waveguides transmitting the power to the dummy load. The gyrotron tests have been temporarily suspended while a new system for the automatic filling of the cryostats with liquid nitrogen and helium is being installed. The experience gained from tests operations including some of the problems related both to auxiliary equipment and to the control of the gyrotrons will be presented with a special focus on long pulse related issues.