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The ECRH system (1.6 MW, 0.5s, 140 GHz) has been widely exploited on FTU (4-8 T; 0.3-1.6 MA; 0.3- 4x10 20 m-3) in the last 10 years. In this paper we report the main recent results obtained applying EC waves for suprathermal current drive, MHD activity control and disruption mitigation. The mostly used suprathermal EC absorption scheme in FTU is at down-shifted frequencies, with central BTo (7 T) higher than the resonant one (5 T). Experiments carried out with Ip=500kA, ne=6-8 1019m-3 and N//EC ranging from 0 to ±0.5 have shown a measured overall current drive (CD) efficiency well above that due to the sum of those expected for the two waves. This fact is ascribed to the existence of a synergy that apparently increases the EC efficiency close to 0.1 1020AW-1m-3. The consequent modification of the current profile is well supported by FEB data. EC waves are the most promising candidate for NTM stabilization/control on ITER. Experiments on real time m=2, n=1 mode stabilization with EC waves are reported, and a description of the control algorithm, based on ECE signals for the detection of the island position and the EC deposition radius, is given. Experiments to study the influence of ECRH power on the disruption evolution have been carried out. The disruptions have been induced by injection of impurities or by increasing the electron density above the Greenwald limit using gas puffing. Magnetic coil measurements and soft-x ray tomography reconstruction results indicate that ECRH is acting on the magnetic island evolution, leading to disruption avoidance and/or to current decay softening, depending on the deposition position. ECRH is found to be effective in disruption avoidance when the deposition location is r/a=0.6 in Mo injection cases and r/a=0 in density limits cases.

This report gives a summary of the activities performed at IFP/CNR during 2003 and 2004/2005 in accrodance with the contract and task agreement between the EUROPEAN ATOMIC ENERGY COMMUNITY and EURATOM/ENEA/CNR ASSOCIATION: Contract EFDA 03/1040 (FU 06-CT-2003-098) Art. 5.1 IDT No JW2-BEP-ENEA-26 The work described in this report is related to the participation in new JET mw-access diagnostic development, with particular reference to the design, construction test and installation of the Quasi-Optical interface boxes, the attendance to the contractual and working Meetings, the final report.

Electron heating, profile control and current drive experiments are performed on FTU tokamak by using a four units EC system at 140, 2 MW total R.F. power. Each unit is composed by a gyrotron with 0.5 MW, 0.5 s pulse length capability, and an hybrid mirror/waveguide system allowing low-loss transmission of the millimeterwave power, with full control of the e.m. field polarization. FTU plasmas are illuminated from the low magnetic field side by four narrow gaussian beams, each one quasi-optically coupled to the correspondent waveguide. The launching system is capable of poloidal/toroidal beam steering through a set of tiltable in-vacuum mirrors, all placed outside the toroidal magnet. Up grading to 1 MW per line is under evaluation.

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