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Abstract:
The current flow to flat Langmuir probes mounted flush into divertor target plates or limiter in a tokamak is studied with particle-in-cell simulations. The simulation model is two- dimensional in real space and three-dimensional in velocity space resolving the gyration of electrons and ions. The following two effects are studied: (i) The lack of saturation of the ion current at grazing incidence of the magnetic field. Simulations are performed with realistic values of the dimensionless parameters (ratios between probe size, gyroradius and Debye length) and the grazing angle of the magnetic field. (ii) The influence of the self-consistent ExB drift. A contribution to the ion current nonsaturation (at negative bias) is found as well as a reduction of the electron current (at positive bias). (C) 2002 American Institute of Physics.
