Magnetic smear effects on confinement and electron heat transport in Tore Supra discharges with electron heating

Various steady state non-inductive plasmas, with strong electron heating and significant modification of the current density profile, have been routinely obtained in Tore Supra discharges with lower hybrid current drive (LHCD) and/or fast wave electron heating (FWEH) experiments. The dependence of the electron heat diffusivity chi(e) on the electron temperature gradient del T-e, the magnetic shear s and the safety factor q is demonstrated. The increase of chi(e) with del T-e indicates the existence of a critical temperature gradient. Moreover, the current density profile affects the global confinement and the local transport. The electron heat flux q(e) is found to be roughly proportional to q(2). The effect of magnetic shear on chi(e) is studied in the improved confinement discharges obtained by modifying the current profile. When the magnetic shear increases in the confinement zone and/or vanishes in she plasma centre, chi(e) decreases. The effect of the current profile is also observed in the saturated ohmic regime. The results for chi(e) do not agree with the local transport models of Taroni et al, ol Rebut-Lallia-Watkins (RLW) for all ranges of electron heating.