Validity condition for the local sheath impedance boundary condition and a nonlocal generalization

Journal Article · Fri Aug 18 00:00:00 EDT 2023 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/5.0163291· OSTI ID:2004935

Myra, James R. ^[1]; Kohno, Haruhiko ^[2]

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1. Lodestar Research Corporation, Boulder, CO (United States); Lodestar Research Corporation
2. Kyushu Institute of Technology, Fukuoka (Japan)

ICRF sheaths can cause unwanted interactions of high-power RF waves with material surfaces in magnetic fusion devices. In previous work, a local RF sheath impedance boundary condition (BC) was derived for use in ICRF codes together with a microscale (i.e., Debye or sheath width scale) model for obtaining the sheath impedance used in that BC. This local RF sheath BC matches the normal component of current and electrostatic potential across the sheath-plasma interface. Collapsing the matching conditions at the sheath-plasma interface to a BC depends on the assumption of scale separation, which can be violated when conditions along the local radius of curvature of the surface vary sufficiently rapidly. The validity condition is explored in this contribution, with special attention to the case where the magnetic field approaches being tangent to the surface. When the local sheath BC no longer applies, a non-local sheath BC is developed under the assumption of a more relaxed scale separation assumption. It is shown that the non-local sheath BC reduces to the previous local sheath BC under appropriate conditions. Furthermore, a surface-integrated sheath admittance parameter describes the 2D physics in the new BC.

• Research Organization: Lodestar Research Corporation, Boulder, CO (United States)
• Sponsoring Organization: JSPS KAKENHI; USDOE Office of Science (SC), Fusion Energy Sciences (FES); USDOE Office of Science and Technology (ST)
• Grant/Contract Number: FG02-97ER54392
• OSTI ID: 2004935
• Report Number(s): LRC--22-191
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 2984; ISSN 0094-243X
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ICRF
RF waves
boundary condition
conference
electrostatics
fusion reactors
sheaths
tokamak