The Tore Supra ICRH antennas, built in collaboration with ORNL¹ according to the Resonant Double Loop concept, have been used for many years on different experimental schemes. They have contributed to meet the initial aim of the Tore Supra tokamak : to operate at a plasma current up to 1.7 MA, over 30 seconds or with a heating power higher than 10 MW. Based on the experience gained, the next step, aiming at high power operation up to 25 MW with long pulse discharges (1000 s), is scheduled on Tore Supra.

To achieve this challenge, some parts of the present antenna must be redesigned, in particular, the lateral protections and the matching system. The Faraday screen, with its actively cooled septum, and the current strap already fulfil the new requirements. The vacuum feedthrough and the supporting structure need a slight change of their cooling systems. The new ICRH antenna protection, also designed to be fitted on LHCD launcher, uses an upgraded technology based on Carbon Fibre Composite (CFC) shaped tiles, intimately linked to the actively water cooled heat sink, by Active Metal Casting process². The protection is designed to withstand the nominal thermal load in steady state operation, the Toroidal Pump Limiter³ being considered as main limiter. In order to qualify the design and the fabrication, heat flux tests on CFC high-tech prototype components using the 200 kW Electron Beam facility of CEA/Framatome are to be performed.

The present matching system of ICRH antennas consists of 2 variable vacuum capacitors at each end of the current strap to provide both frequency tuning and impedance matching over a frequency range from 35 to 80 MHz. By construction, such a variable capacitor limits the velocity of the capacitance variation, preventing from matching rapid load variations during transient phenomena like pellet injection, monster sawteeth or plasma displacements. A new concept of matching system, based on sliding contacts and allowing faster capacitance adjustment is now studied. These contacts, already tested at Cadarache have been proved as working at high RF current (1000 Arms, 60 MHz) under high vacuum conditions. The contacts will be incorporated within a variable capacitor or a tuning stub, the latter being transposable on ITER antennas.

The paper will detail the lateral protection and matching systems concept, as well as the results of the heat load tests for the protection, and of RF tests for the matching system.

1 Oak Ridge National Laboratory, Fusion Energy, Tennessee, USA
2 Process developed by Plansee AG- Austria
3 See paper - Toward long pulse performance discharges in Tore Supra- Upgrading of inner vessel components - (CIEL Project) - M. Lipa - This conference.