Latest Achievements of the JET ICRF Systems in View of ITER
During the 2008-2009 JET campaigns, ICRF power was coupled to ELMy H-mode plasmas using 2 distinctly different antenna systems. The newly added ITER-like ICRF antenna aimed in priority at the validation for ITER of high power density load resilient antenna concepts while the A2 antennas were equipped with 2 different load resilient transmission line circuits in order to increase the power coupled to the JET Hmode plasmas. An external conjugate-T junction layout was implemented between the A2 antennas C and D and 3dB hybrid couplers between the A2 antennas A and B. Both load tolerant approaches have demonstrated robust and reliable performance during operations in a variety of plasma loading conditions including on large Type I ELMs. Depending on the plasma scenario, the trip-free time-average power levels coupled to ELMy H-mode plasma during long pulse operations have reached 3.3MW for the 3dB hybrids and 4MW for the external Conjugate-T system. Up to 7MW total ICRF power was coupled to ELMy plasmas simultaneously by all four conventional JET ICRF antennas. The ITER-like ICRF antenna has demonstrated efficient trip-free ELM tolerant operation on ELMy plasmas with power densities up to 6.2MW/m2 on L-mode and 4.1MW/m2 on Hmode with voltages up to 42kV without significant impurity production. It also provided validation of the ICRF coupling modelling code TOPICA confirming that the ITER ICRF system could couple the 20MW requested at a system voltage below 45kV.