Turbulence studies by fast camera imaging experiments in the TJII stellarator

Experimental studies of turbulence and plasma–wall interaction by fast visible imaging in the TJII stellarator are presented. Visualization of low intensity phenomena was possible by the installation of image intensifiers, allowing the direct observation of turbulent transport events in the scrape off layer (SOL). The observation of turbulent structures propagating poloidally at the plasma edge has shown enough periodicity to allow correlation between them with repetition rates around 10 kHz, as a quasicoherent mode. The analysis of plasma–wall interaction by filtered imaging have shown that there is a change in the ‘preferred’ plasma–wall interaction area, going from a hardcore toroidally limited plasma to a poloidally locally limited one in the transition from ECRH to NBI heated plasmas.