Long-pulse plasmas created in the Chinese Experimental Advanced Superconducting Tokamak (EAST) mark another advance in fusion. EAST demonstrates a method for controlling the instabilities at the plasma edge that might otherwise limit the performance of prototypical fusion power plants such as ITER. CEA Researchers were involved through international collaboration.
One of the challenges for the magnetic fusion is to master long-pulse and high performance plasmas, though careful control of the heat loads generated by edge instabilities (known as Edge Localized Modes, or ELMs), and deposited onto the plasma facing components. A high-confinement plasma regime (representative of the ITER baseline plasma) has been recently obtained on the EAST tokamak (ASIPP, Chinese Academy of Sciences, Hefei, Anhui Province, People Republic of China) with a world record duration exceeding 30 s (Figure).
The plasma magnetic configuration is sustained for more than 30s by radio-frequency wave injection (lower hybrid current drive, LHCD), the tokamak wall being pre-conditioned by advanced techniques using lithium. The heat load minimization and the edge instability mitigation result from a local ergodization of the plasma edge magnetic configuration by LHCD, and small scale turbulence generated by supersonic molecular beam injection (SMBI).
The results are published in Nature Physics (17 Nov. 2013). Scientists from the Institute for Magnetic Fusion Research (CEA, Physical Sciences Division) brought their experience in ELM mitigation techniques and power deposition control experiments. Lower hybrid waves are indeed routinely used on the Tore Supra tokamak at CEA/Cadarache for sustaining long pulse operation, and considered for ITER as an upgrade. Cooperation between CEA/IRFM and ASIPP was recently strengthened with the creation of an Associated Laboratory in the field of Fusion, agreement signed by the Director of Physical Sciences Division, G. Fioni, on 03 July 2013.
Fait marquant rédigé par X.L ZOU.
Maj : 08/01/2014 (345)