An Heuristic Drift-Based Model of the Power Scrape-Off Width in H-Mode Tokamaks

Robert J. Goldston

关键词: CONFINEMENT TIME;    DIVERTORS;    ELECTRONS;    FORECASTING;    HEAT FLUX;    MODIFICATIONS;    PLASMA;    PLATES;    POWER INPUT;    SOLS;    THERMAL CONDUCTION;    THERMAL DIFFUSIVITY Tokamaks;    H-Mode;   

DOI  :  10.2172/1007202
RP-ID  :  PPPL-4604
PID  :  OSTI ID: 1007202
Others  :  TRN: US1101496

学科分类：原子、分子光学和等离子物理

美国|英语

来源: SciTech Connect

【 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 mass flow pattern posited is a modification for open field lines of Pfirsch-Shl??ter flows to include sinks to the divertors. These assumptions result in an estimated SOL width of 2a??p/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-H?��rm parallel thermal conduction losses to the divertor. This results in an heuristic closed-form prediction for the power scrape-off width that is in remarkable quantitative agreement both in absolute magnitude and in scaling with recent experimental data. Further work should include full numerical calculations, including all magnetic and electric drifts, as well as more thorough comparison with experimental data.