ECCD experiments in Heliotron J. Recent results regarding the dependence on magnetic configuration and wave polarization

The electron cyclotron current drive (ECCD) is investigated in Heliotron J for two new magnetic configurations with ECRH heating located at the ripple top and the ripple bottom, respectively, using different incoming wave polarizations. The results are compared with the previous ECCD experiments, performed in the low, medium (standard) and high bumpiness configurations, where a sign reversal of the EC current is observed between the ripple top and the ripple bottom heating conditions. It is shown here that a similar behaviour is obtained in the new configurations. Positive currents are obtained when the ECR heating is located at the magnetic field minimum, whereas negative currents, but not higher in magnitude than the ones obtained in the previous experiments, appear with ripple top heating. The dependence of the ECCD on the polarization of the injected waves agrees with the expected behaviour. (author)