Plasma sheath transmission factors for tokamak edge plasmas

Journal Article · Thu Mar 01 04:00:00 EST 1984 · Phys. Fluids; (United States)

DOI:https://doi.org/10.1063/1.864677· OSTI ID:5117692

Stangeby, P C

Simple analytic relations are derived for the floating potential of a solid object in contact with a magnetized plasma as a function of the electron/ion mass ratio, the electron/ion temperature ratio, and the secondary electron emission coefficient. Simple analytic relations are also obtained for the sheath transmission factors, i.e., the particle and energy fluxes to floating and nonfloating surfaces. These analytic formulations, derived from a fluid model treatment of ion flow, are found to give results in close agreement with results derived from more complex analysis based on kinetic theory and numerical models. Tokamak scrape-off plasmas are often characterized by ion distributions which have finite drift velocities at the point where the ions enter the scrape-off plasma from the main plasma (via cross-field diffusion). The Bohm criterion governing the drift velocity of ions as they enter the electrostatic sheath in front of a limiter, divertor plate, or probe is generalized for this case.

• Research Organization: University of Toronto, Institute for Aerospace Studies, Downsview, Ontario, Canada M3H 5T6 and UKAEA (Euratom/UKAEA Fusion Association) Culham Laboratory, Abingdon, Oxon, OX14 3DB, United Kingdom
• OSTI ID: 5117692
• Journal Information: Phys. Fluids; (United States), Journal Name: Phys. Fluids; (United States) Vol. 27:3; ISSN PFLDA
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700102* -- Fusion Energy-- Plasma Research-- Diagnostics
BOHM CRITERION
BOUNDARY LAYERS
CLOSED PLASMA DEVICES
DISTRIBUTION
DIVERTORS
ION DRIFT
LAYERS
LIMITERS
MAGNETIZATION
PHYSICAL PROPERTIES
PLASMA DIAGNOSTICS
PLASMA SCRAPE-OFF LAYER
PLASMA SHEATH
POTENTIALS
PROBES
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
WALLS