Expanding the operating space of ICRF on JET with a view to ITER

Full text: The size and capability of JET to confine very energetic particles, together with its versatile ICRF system, provide a unique environment to develop ICRF techniques relevant to the Next Step. During the 2003-2004 experimental campaigns, in addition to further development of ICRF as a tool for the JET experimental programme, several heating and current drive scenarios have been investigated, contributing to the physics understanding and operational expertise required for successful use of ICRF on ITER: heating and current drive in hydrogen plasmas for the low activation phase of ITER, minority heating of tritium, experimental demonstration of Larmor radius effects in the second harmonic heating scenario, direct electron heating and current drive, new results on ICRF heating efficiency. The first part of the paper reports on these advances. The second part presents studies of a more technical nature: studies of ELMs using fast RF measurements, and the proof of principle of a new ELM-tolerant antenna matching scheme. Finally, the last part of the paper reviews the technical enhancements planned on the JET ICRF system, the major component being the new ITER-like antenna. (author)