Effects of ICRH on electrostatic fluctuations and particle transport in the boundary plasma of TEXTOR

Abstract

Direct current (DC) driven and turbulence driven cross-field particle fluxes have been deduced from Langmuir probe measurements during discharges with ion cyclotron resonance heating (ICRH) in the TEXTOR tokamak. Spectral analysis of fluctuations of the floating potential at spatially separated probe pins has been used to determine the velocity associated with the poloidal rotation of the boundary plasma. Characteristics of the turbulence spectra of density and potential fluctuations at the edge during ICRH have been measured and compared with the corresponding spectra during standard ohmically heated discharges. It has been observed that both DC driven and turbulence driven fluxes increase significantly during ICRH. The measured high particle fluxes indicate motion in DC convective cells. The DC convective flux and the turbulence driven flux are partly counteracting.