Electron heat transport properties have been investigated by means of localized steady-state and modulated electron cyclotron heating in the ASDEX Upgrade tokamak. The experimental findings have been successfully compared with the model assumption of a threshold gradient length, L/sub Tc/, (1/L/sub T/ = - nabla T/sub e0//T/sub e0/), in the electron temperature T /sub e0/ below which the electron thermal conductivity measured under steady-state conditions, chi /sub ePB/, shows a sudden increase and the heat conduction `seen' by a temperature perturbation, chi /sub eHP/, switches from low to high values. In this work electron cyclotron heating (ECH) power is used both to modify the steady-state gradient length and to induce a nonlinear transition from low to high electron heat transport at the position where the temperature gradient crosses its critical (or threshold) value. Steady-state ECH has been injected at different radial positions and the changes induced in electron heat transport have been studied by means of cold pulses launched from the plasma boundary. Cold pulses, obtained by injecting radiating impurities by means of laser blow off of silicon, have proved to be a flexible tool for investigating both the radial position of the step in chi /sub eHP/ and the dependence on local plasma parameters of the underlying physical mechanism.
|Titolo:||Nonlinear pertubative electron heat transport study in the ASDEX upgrade tokamak|
|Autori interni:||DE LUCA, FRANCA (Secondo)|
|Parole Chiave:||Experimental/ plasma impurities; plasma instability; plasma radiofrequency heating; plasma temperature; plasma toroidal confinement; plasma transport processes; Tokamak devices/ nonlinear perturbative electron heat transport; ASDEX Upgrade tokamak; localized steady-state electron cyclotron heating; modulated electron cyclotron heating; threshold gradient length; electron temperature; electron thermal conductivity; heat conduction; temperature perturbation; steady-state gradient length; critical temperature; plasma boundary; impurity injection; laser blow off; local plasma parameters; Si/ A5225F Plasma transport properties A5235M Nonlinear plasma waves and nonlinear interactions A5255G Plasma in torus (stellarator, tokamak, etc.) A5250G Plasma heating A5235P Plasma instabilities A5225L Plasma temperature and density A5240H Solid state-plasma interactions/ Si/el|
|Settore Scientifico Disciplinare:||Settore FIS/01 - Fisica Sperimentale|
|Data di pubblicazione:||2005|
|Digital Object Identifier (DOI):||10.1088/0029-5515/45/1/005|
|Appare nelle tipologie:||01 - Articolo su periodico|