Characterization of the edge turbulence and electron profiles in TCV tokamak with the Thermal Helium Beam diagnostic

A Thermal Helium Beam diagnostic, recently installed on TCV, allows measurement of the radial profiles of electron density and temperature at the outboard midplane edge and Scrape Off Layer, together with their high frequency turbulent fluctuations up to 200 kHz. The edge region is studied for a range of L-mode discharges, with different heating schemes: purely ohmic, with Neutral Beam injection and/or Electron Cyclotron heating. Edge profiles are strongly modified by auxiliary heating, and the changes in the gradients of the electron density and pressure are linked to those in the turbulence behaviour: fluctuation levels and blob dimensions are found to be strongly correlated with the characteristic radial lengths of the profiles. A comparison with H-mode discharges is also discussed, in terms of inter-ELM turbulence and local gradients.