Evidence for edge gradients as control parameters of the spontaneous high-mode transition

Citation
Rj. Groebner et al., Evidence for edge gradients as control parameters of the spontaneous high-mode transition, PHYS PLASMA, 8(6), 2001, pp. 2722-2730
Citations number
32
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physics
Journal title
PHYSICS OF PLASMAS
ISSN journal
1070-664X → ACNP
Volume
8
Issue
6
Year of publication
2001
Pages
2722 - 2730
Database
ISI
SICI code
1070-664X(200106)8:6<2722:EFEGAC>2.0.ZU;2-R
Abstract
Measurements in the DIII-D tokamak [J. L. Luxon , Plasma Physics and Contro lled Fusion Research, 1986 (International Atomic Energy Agency, Vienna, 198 7), Vol. I, p. 159] show that edge gradients of ion and electron temperatur e and pressure, delT(i), delT(e), delP(i), and delP(e), are good candidates for parameters which respond to the heating power to control the fundament al physics of the spontaneous Low-mode (L-mode) to High-mode (H-mode) trans ition. These gradients are measured in the region where the H-mode transpor t barrier forms and they are found to consistently increase in time during the L-phase of discharges which make a transition to H-mode. Moreover, for a fixed magnetic configuration, there is a well-defined boundary between th e L-mode and H-mode states in the delT(e)-delP(e) operational space. The va lues of T-i, T-e, P-i, and P-e, measured at this location, show smaller rel ative changes during the L-phase of these discharges, indicating that the s cale lengths of these quantities are decreasing as the L-H transition is ap proached in time. These results are consistent with several theoretical mod els in which gradients of pressure or temperature cause the transition. (C) 2001 American Institute of Physics.