Effect of rotating helical magnetic field on the turbulence fractal structure and transport in the tokamak edge

Plasma edge fluctuations measured with Langmuir probe in relation to the turbulence structure and associated enhanced transport have been studied in the tokamak HYBTOK-II with a variation of the rotating helical magnetic field (RHF) frequency in the range of 5–30 kHz. Edge fluctuations have non-Gaussianity statistics caused by intermittent bursts with time scale of 40–100 μs. The variation in the RHF frequency has a selective effect on the edge turbulent fractal structure and the turbulent flux, demonstrating a selective control of the transport process. A delayed synchronization control of resonant drift wave modes by the RHF is considered as a candidate mechanism to explain the RHF frequency dependence of the edge turbulent fractal structure.