Development of RF Tools and Scenarios for ITER on JET
The improvement of LH coupling with local puffing of D2 gas, which made operation at ITER relevant distances (10cm) and with ELMs a reality, has been extended to ITER- like plasma shapes with higher triangularity. With ICRF, we developed tools such as (1) localized direct electron heating using the 3He mode conversion scenario for electron heat transport studies, (2) the production of 4He ions with energies in the MeV range by 3 wc acceleration of beam injected ions at 120 keV to investigate Alfven instabilities and test a diagnostics, (3) the stabilisation and destabilisation of sawteeth and (4) ICRF as as a wall conditioning. Several ITER relevant scenarios were tested. The (3He)H minority heating scenario, considered for the non-activated start-up phase of ITER, produces at very low concentration energetic 3He which heat the electrons indirectly. For n3He/ne > 2%, the scenario transforms to a mode conversion scenario where the electrons are heated directly. The (D)H minority heating is not accessible as the concentration of C6+ dominates the wave propagation and always leads to mode conversion. The minority heating of T in D is very effective heating for ions and producing neutrons. New results were obtained in several areas of ICRF physics. Experimental evidence confirmed the theoretical prediction that, as the larmor radius increases beyond 0.5 times the perpendicular wavelength of the wave, the second harmonic acceleration of the ions decreases to very small levels. An exotic fusion reaction (pT) must be taken into account when evaluating neutron rates. The contribution of fast particles accelerated by ICRF to the plasma rotation was clearly identified, but it is only part of an underlying, and not yet understood, co-current plasma rotation. Progress was made in the physics of ELMs while their effect on the ICRF coupling could be minimized with the conjugate-T matching scheme. The addition of 3dB couplers is a step in increasing the power capability of the ICRF heating on JET in ELMy plasmas. The installation of an ITER-like, ELM resilient antenna in 2006 will further improve this and be a test of the ICRF scheme for ITER.