ITER ICRF antenna analysis and optimization using the TOPICA code

This paper documents the complete analysis and optimization of the ITER ion cyclotron range of frequency (ICRF) launcher using the TOPICA code, carried out in the frame of EFDA design activities. The possibility to simulate the detailed geometry of an ICRF antenna in front of a realistic plasma description and to obtain the antenna input parameters and the radiated near electric field distribution is of paramount importance to evaluate and predict the overall system performances. Upon starting from a reference geometry, we pursued a detailed electrical optimization of the IC launcher and we came out with a final geometry showing a remarkable increase in terms of power coupled to plasma. The optimization procedure involved the modification of different parts of the antenna, such as the horizontal septa, the coaxial cables, the coax-to-feeder transitions, the feeders, the strap and the grounding. Eventually, the optimized geometry has been the object of a comprehensive analysis, varying the working frequency, the plasma conditions and the poloidal and toroidal phasings between the feeding cables. The performances of the antenna have been appreciated not only in terms of input parameters or power coupled to plasma, but also by means of power spectra and with the evaluation of the RF potentials.