Sheath Physics and Boundary Conditions for Edge Plasmas

• Published in: Contributions to plasma physics (1985) Vol. 44; no. 1-3; pp. 111 - 125
• Main Authors: Cohen, R. H., Ryutov, D. D.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Berlin WILEY-VCH Verlag 01.04.2004; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: Boundary conditions; edge; Exact sciences and technology; Magnetic confinement and equilibrium; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; plasma; Plasma interactions (nonlaser); Plasma properties; Plasma simulation; Plasma-wall interactions; boundary layer effects; sheath; Transport properties; Plasma simulation; Magnetic confinement; Theoretical study; Boundary conditions; Plasma transport processes; Confined plasma; Plasma sheaths; Plasma boundary layers; Plasma radial profiles; Plasma fluid equations
• ISSN: 0863-1042; 1521-3986
• DOI: 10.1002/ctpp.200410016

The boundary conditions of mass, momentum, energy, and charge appropriate for fluid formulations of edge plasmas are surveyed. We re‐visit the classic problem of 1‐dimensional flow, and note that the “Bohm sheath criterion” is requirement of connectivity of the interior plasma with the external world, not the result of termination of the plasma by a wall. We show that the nature of the interior plasma solution is intrinsically different for ion sources that inject above and below the electron sound speed. We survey the appropriate conditions to apply, and resultant fluxes, for a magnetic field obliquely incident on a wall, including the presence of drifts and radial transport. We discuss the consequences of toroidal asymmetries in wall properties, as well as experimental tests of such effects. Finally, we discuss boundary‐condition modifications in the case of rapidly varying plasma conditions. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)