Recent developments in steady-state physics and technology of tokamaks in Cadarache

摘要

Operation of Tore Supra has resumed after a major upgrade of internal components in order to increase the heat extraction capability to 25 MW for 1000 s and address long-pulse research at the level of power density flowing through the last closed flux surface relevant for the next step. This overview highlights first the related technology developments: industrial realization and tests with plasma of about 600 limiter components made of some 12 000 actively cooled CFC tiles. World record breaking discharges with a coupled (and extracted) energy of 0.74 GJ have been obtained, with durations exceeding 4 min, limited only by the long-pulse capability of the heating and current drive systems. Particle balance analysis shows that the in-vessel deuterium inventory never reached saturation. For the same plasma parameters, the in-vessel inventory is reduced by a factor of ≈2 when efficient supersonic gas injection is used. New physics is observed when the loop voltage vanishes for long times: the density remains peaked in spite of the absence of the Ware pinch effect, and, independently, the response to additional heating becomes dominated by a complex interplay between transport and current drive. The contributions of the EURATOM-CEA Association to fusion energy research also include new developments in the field of plasma-facing components, negative ion beam injection (1000 s H~- source and SINGAP acceleration to 1 MeV) and superconductors (cable in conduit concept, connections, testing). Finally, European studies for Cadarache as a site for ITER conclude that all ITER technical requirements are met.