Heuristic Drift-based Model of the Power Scrape-off width in H-mode Tokamaks

Goldston, Robert J.

Princeton University. Plasma Physics Laboratory.

关键词: Thermal Diffusivity Divertors, Edge Plasma, Finite Larmor Effects,Transport Theory, Tokamaks, Plasma-Wall Interaction, Scaling Laws, Scrape-Off Layaer (Sol);    Heat Flux;    Forecasting;    Modifications;    70 Plasma Physics And Fusion Technology;   

DOI  :  10.2172/1013252
RP-ID  :  PPPL-4619
RP-ID  :  DE-ACO2-09CH11466
RP-ID  :  1013252

美国|英语

来源: UNT Digital Library

【 摘 要 】

An heuristic model for the plasma scrape-off width in H-mode plasmas is introduced. Grad B and curv B drifts into the SOL are balanced against sonic parallel flows out of the SOL, to the divertor plates. The overall particle flow pattern posited is a modification for open field lines of Pfirsch-Shlüter flows to include sinks to the divertors. These assumptions result in an estimated SOL width of ~ 2aρp/R. They also result in a first-principles calculation of the particle confinement time of H-mode plasmas, qualitatively consistent with experimental observations. It is next assumed that anomalous perpendicular electron thermal diffusivity is the dominant source of heat flux across the separatrix, investing the SOL width, defined above, with heat from the main plasma. The separatrix temperature is calculated based on a two-point model balancing power input to the SOL with Spitzer-Härm parallel thermal conduction losses to the divertor. This results in a heuristic closed-form prediction for the power scrape-off width that is in reasonable quantitative agreement both in absolute magnitude and in scaling with recent experimental data from deuterium plasmas. Further work should include full numerical calculations, including all magnetic and electric drifts, as well as more thorough comparison with experimental data.