Ion velocity distributions at the tokamak edge

Journal Article · Tue Oct 01 00:00:00 EDT 1991 · Physics of Fluids B; (United States)

DOI:https://doi.org/10.1063/1.859919· OSTI ID:5176337

Pitts, R A ^[1]

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1. AEA Fusion, Culham Laboratory, UKAEA/Euratom Fusion Association, Abingdon, Oxfordshire OX14 3DB (United Kingdom)

This paper compares the form of {ital f}({ital v}{sub {parallel}}) arising from the warm-ion, kinetic models of Emmert {ital et} {ital al}. (Phys. Fluids {bold 23}, 803 (1980)) and Bissel and Johnson (Phys. Fluids {bold 30}, 779 (1987)) with experimentally measured distributions from the DITE tokamak obtained with a retarding field analyzer (RFA). The results show that the commonly adopted assumption of a distribution accelerated through the sheath potential and approximating to a Maxwellian in the high-energy tail is reasonable. In this respect, Emmert's distribution is more appropriate. In addition, the common practice of neglecting the presheath effect on the distribution is generally justified in analyzing the RFA characteristic, but may incur large error under some circumstances. While the comparison also illustrates how differing assumptions regarding the source function can have a reasonably strong influence on the ion velocity distribution at walls and limiters, the integrated distributions required for comparison with RFA data are sufficiently similar that distinguishing between the models experimentally is not generally possible. The problems of resolving these differences experimentally are discussed and suggestions are proposed for further experiments.

• OSTI ID: 5176337
• Journal Information: Physics of Fluids B; (United States), Vol. 3:10; ISSN 0899-8221
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
DITE TOKAMAK
PLASMA SHEATH
MAGNETIC FIELDS
PLASMA DRIFT
PLASMA
DISTRIBUTION FUNCTIONS
BOLTZMANN STATISTICS
COMPARATIVE EVALUATIONS
END EFFECTS
FLUCTUATIONS
IONS
KINETIC EQUATIONS
ONE-DIMENSIONAL CALCULATIONS
PLASMA SIMULATION
VELOCITY
WALLS
CHARGED PARTICLES
CLOSED PLASMA DEVICES
EQUATIONS
EVALUATION
FUNCTIONS
SIMULATION
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
VARIATIONS
700103* - Fusion Energy- Plasma Research- Kinetics