Quasi‐coherent Oscillations in the TJ‐II Stellarator

Quasi‐coherent oscillations have been observed in TJ‐II plasma with different diagnostics: Heavy Ion Beam Probe (HIBP), ECE, Langmuir probes and Mirnov coils. A recent improvement in the signal to noise ratio of the HIBP allowed us to observe the radial structure of these oscillations from the edge to the plasma core. The edge quasi‐coherent fluctuations have been observed in some configurational windows, when the ratio of plasma density to heating power is above a threshold.