Comparison of the performance of different options for ITER ECRH Upper Launcher

The performance of different options for the ITER ECRH upper launcher is analysed in terms of NTM stabilisation efficiency, which is the main task for this system. The driven current at the (3,2) and (2,) resonant surfaces of ITER scenarii 2, 3a and 5 is calculated and compared with the local bootstrap current density there, which is the drive for the NTM. It is found that in terms of the figure of merit for NTM stabilisation, jECCD/jbs, a launcher concept based on front steering has much better performance than concepts based on remote steering. This can be explained by the smaller spot size of the ECRH beam at the resonant surfaces in the case of front steering. Thus, from a physics point of view, the analysed front steering option is preferable to the remote steering option.