FINAL TESTS ON THE FTU LHRF PROTOTYPE COUPLING STRUCTURE

The FTU 8 GHz lower hybrid antenna is an assembly of 3 standard grills each with 4×12 waveguides. Three of the antennas will feed three equatorial ports of FTU. The main goal is to routinely inject RF into the plasma at very high power density (> 10 kW/cm 2 ), as already demonstrated on the FT preliminary experiments. Due to the FTU narrow accesses and n‖ requirements, the FTU antennas present advanced technological solutions such as the multiwindow flange (48 bricks of Al 2 O 3 brazed on a Ti alloy frame with overall dimensions 13.7×9 cm 2 ). To test the power capability, each grill of the first antenna has been successfully processed at nominal RF power with a large number of RF pulses, while destructive tests have been performed on the more critical items to ascertain their limits. Results of these tests will be reported together with the RF measurements needed to characterize the whole prototype.