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Title: Bohm criterion and plasma particle/power exhaust to and recycling at the wall

The plasma particle and power exhaust to the divertor surface drives both particle and power recycling at the surface, which in return constrains the plasma density and temperature at the target and their profile further upstream. Both particle and power exhaust fluxes are mediated by the plasma sheath next to the divertor surface. In particular, the Bohm criterion constrains the ion exit flow speed, which enters directly into the particle flux and the kinetic flow energy component of the ion power flux, and indirectly into the electron power flux through the sheath potential drop. Here we give an overview on how the Bohm speed is set in a general plasma and how it enters power exhaust and power recycling at the divertor surface, and the implication on the correct implementation of sheath boundary conditions in numerical codes. The cases of ideal and non-ideal Bohm speed are distinguished as a result of the physics discussion.
Authors:
ORCiD logo [1] ; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
LA-UR-16-24857
Journal ID: ISSN 2352-1791
Grant/Contract Number:
AC52-06NA25396
Type:
Published Article
Journal Name:
Nuclear Materials and Energy
Additional Journal Information:
Conference: International Conference on Plasma Surface Interactions in Controlled Fusion Devices , Rome (Italy), 30 May 2016; Journal ID: ISSN 2352-1791
Publisher:
Elsevier
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC). Advanced Scientific Computing Research (ASCR) (SC-21); USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Magnetic Fusion Energy; Bohm criterion; Ideal Bohm speed; Non-ideal Bohm speed; Plasma particle exhaust; Plasma power exhaust; Power recycling; Ion reflection
OSTI Identifier:
1361705
Alternate Identifier(s):
OSTI ID: 1369183