A calculation model for density limits in auxiliary heated, gas fueled tokamaks and application to DIII-D model problems

Authors
Citation
Wm. Stacey, A calculation model for density limits in auxiliary heated, gas fueled tokamaks and application to DIII-D model problems, PHYS PLASMA, 8(8), 2001, pp. 3673-3688
Citations number
43
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physics
Journal title
PHYSICS OF PLASMAS
ISSN journal
1070-664X → ACNP
Volume
8
Issue
8
Year of publication
2001
Pages
3673 - 3688
Database
ISI
SICI code
1070-664X(200108)8:8<3673:ACMFDL>2.0.ZU;2-C
Abstract
A model for the calculation of density limits in high confinement (H-mode) tokamaks is described. The model consists of coupled calculations of (1) th e power, particle and momentum balances for the core plasma and for the div ertor/SOL (scrape-off layer) plasma; (2) the transport of fueling and recyc ling neutrals; (3) pedestal gradient scale lengths and MHD (magnetohydrodyn amic) limits; (4) confinement degradation due to thermal instabilities in t he edge transport barrier; (5) divertor and core MARFE (multifaceted asymme tric radiation from edge) onset; (6) radiative collapse leading to disrupti on, and (7) power threshold for high-to-low mode transition. The model is a pplied to study the effects of different operational parameters (e.g., P, I , B) on the density limit for auxiliary heated, gas fueled DIII-D [J. L. Lu xon, F. Batty, C. B. Baxi , Plasma Physics and Controlled Nuclear Fusion Re search 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] model problems. Predicted values of densities, temperatures, and edge gradient scale length are generally consistent with measured values, and ma ny of the phenomena observed experimentally in association with density lim its are predicted. It is found that the MARFE density limit increases stron gly with increasing auxiliary heating power per unit plasma surface area (i .e., power flux exiting the core into the SOL) and with increasing plasma c urrent, and decreases weakly with increasing magnetic field and with increa sing carbon impurity concentration. (C) 2001 American Institute of Physics.