Experimental and neoclassical electron heat transport in the LMFP regime for the stellarators W7‐A, L‐2, and W7‐AS

Abstract

The electron energy balance is analyzed for equivalent low‐density electron cyclotron resonance heated (ECRH) discharges with highly peaked central power deposition in the stellarators W7‐A [Plasma Phys. Controlled Fusion 28, 43 (1986)], L‐2 [Proceedings of the 6th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Berchtesgaden, 1976 (International Atomic Energy Agency, Vienna, 1977), Vol. 2, p. 115] and W7‐AS [Proceedings of the 9th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Baltimore, 1982 (International Atomic Energy Agency, Vienna, 1983), Vol. 3, p. 141]. Within the long mean‐free path (LMFP) collisionality regime in stellarators, the neoclassical electron heat diffusivity χe can overcome the ‘‘anomalous’’ one. The neoclassical transport coefficients are calculated by the dkes code (Drift Kinetic Equation Solver) [Phys. Fluids 29, 2951 (1986); Phys. Fluids B 1, 563 (1989)] for these configurations, and the particle and energy flu...