ECCD calculations in ITER by means of the quasi-optical code

Electron cyclotron current drive (ECCD) calculations for the case of the ITER electron cyclotron resonant heating upper port launcher are presented making use of a quasi-optical (QO) code (Balakin et al 2008 Nucl. Fusion 48 065003). The QO code describes accurately the behaviour of the wave beam in the electron cyclotron resonance layer, taking into account spatial inhomogeneity and dispersion. The ECCD efficiency is obtained using the adjoint calculation as presented by (Lin-Liu et al 2003 Phys. Plasmas 10 4064). The results show a broadening of the EC driven current density profiles in the range 15-30% as compared with beam-tracing calculations using TORBEAM. Consistently, peak driven current density values are found to be decreased by 10-20%. These results have significant consequences for the determination of the requirements on ECCD power to control magnetohydrodynamic instabilities such as neoclassical tearing modes and sawteeth.