Abstract
The plasma edge of the CASTOR tokamak was investigated using a thermal lithium beam and electrical probes. The density profiles in the scrape-off layer (SOL) obtained by means of the lithium beam technique clearly reflect the particular limiter configuration and allow the evaluation in terms of D⊥. These profiles are in good agreement with simultaneous Langmuir probe measurements at different radii. In discharges with additional lower hybrid current drive (OH/LHCD) steeper profiles are obtained, which indicates a reduced radial particle transport. This is supported by the evaluation of fluctuation measurements (density and poloidal electric field) in terms of the turbulent radial particle flux, and by a reduced temporal decay of the line-averaged density during RF. Thus, in effect LHCD improves the particle confinement.
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