Non-existence of Normal Tokamak Equilibria with Negative Central Current

Hammett, G.W. ; Jardin, S.C. ; Stratton, B.C.

Princeton University. Plasma Physics Laboratory.

关键词: Non-Inductive Current Drive;    Equilibrium, Mhd-Toroidal;    70 Plasma Physics And Fusion Technology;    Virial Theorem;    Current Density;   

DOI  :  10.2172/812029
RP-ID  :  PPPL-3788
RP-ID  :  AC02-76CH03073
RP-ID  :  812029

美国|英语

来源: UNT Digital Library

【 摘 要 】

Recent tokamak experiments employing off-axis, non-inductive current drive have found that a large central current hole can be produced. The current density is measured to be approximately zero in this region, though in principle there was sufficient current-drive power for the central current density to have gone significantly negative. Recent papers have used a large aspect-ratio expansion to show that normal MHD equilibria (with axisymmetric nested flux surfaces, non-singular fields, and monotonic peaked pressure profiles) can not exist with negative central current. We extend that proof here to arbitrary aspect ratio, using a variant of the virial theorem to derive a relatively simple integral constraint on the equilibrium. However, this constraint does not, by itself, exclude equilibria with non-nested flux surfaces, or equilibria with singular fields and/or hollow pressure profiles that may be spontaneously generated.