STUDY OF 70GHZ SECOND HARMONIC X-MODE ECCD IN HELIOTRON J
This work is performed with the support and under the auspices of the Collaboration Program of the Laboratory for Complex Energy Processes, IAE, Kyoto University, and the NIFS Collaborative Research Program (NIFS04KUHL005, NIFS08KOAR010), the NIFSININS project of Formation of International Network for Scientific Collaborations, and the Grant-in-Aid for Scientific Research, MEXT.
Second harmonic X-mode electron cyclotron current drive (ECCD) experiments have been made in Heliotron J by using an upgraded EC launching system. A focused Gaussian beam is injected with the parallel refractive index, N‖, ranging from -0.05 to 0 6. According to ray tracing calculations, the focused Gaussian beam makes the EC power absorption localized, Δρ<0.2, modifying the rotational transform profile. The experimental results show that the EC driven current can be controlled by N‖ and it depends on the local magnetic field structure where the EC power is deposited. A large increase in ECE signals has been observed when the EC current was driven, indicating important role of high-energy electrons on the ECCD.
