Coupling between turbulence and flows during edge transport barrier formation and collapse

The coupling between sheared flows and density turbulence has been studied experimentally by means of Doppler reflectometry during the L-H and H-L transitions in the TJ-II stellarator. Measurements performed during the L-H transition indicate that the mean sheared flow is not the unique element to explain the suppression of turbulence, oscillating sheared flow has to be also considered. At the H-L back transition, the spatio-temporal evolution of turbulence and flows shows signatures of spatial spreading of the turbulence.