Fast electron transport in lower-hybrid current drive
- Plasma Fusion Center and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts (USA)
The quasilinear Fokker--Planck formulation is generalized for lower-hybrid current drive to include the wave-induced radial transport of fast electrons. Toroidal ray tracing shows that the wave fields in the plasma develop a large poloidal component associated with the upshift in {ital k}{sub {parallel}} and the filling of the spectral gap.'' These fields lead to an enhanced radial {ital E}{times}{ital B} drift of resonant electrons. Two types of radial flows are obtained: an outward convective flow driven by the asymmetry in the poloidal wave spectrum, and a diffusive flow proportional to the width of the poloidal spectrum. Numerical results relevant to Alcator C (Phys. Rev. Lett. {bold 53}, 450 (1984)) and JT-60 (Nucl. Fusion {bold 29}, 1815 (1989)) are presented; they show that the radial convection velocity has a broad maximum of nearly 1 m/sec and is independent of the amplitude of fields. In both cases, the radial diffusion is found to be highly localized near the magnetic axis. For JT-60, the peak of the diffusion profile can be quite large, nearly 1 m{sup 2}/sec.
- DOE Contract Number:
- FG02-91ER54109
- OSTI ID:
- 5216835
- Journal Information:
- Physics of Fluids B; (United States), Vol. 3:10; ISSN 0899-8221
- Country of Publication:
- United States
- Language:
- English
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