Propagation of neutralized plasma beams

Wessel, F. J.; Rostoker, N.; Fisher, A.; Rahman, H. U.; Song, J. H.
June 1990
Physics of Fluids B: Plasma Physics;Jun90, Vol. 2 Issue 6, p1467
Academic Journal
Beams of neutralized plasma will cross a transverse magnetic field, magnetized plasma, and neutral gas, by a combination of single particle and collective-plasma processes. At low density the beam will deflect; at higher density the beam will exhibit undeflected motion by the E x B drift or diamagnetic (high-beta) exclusion of the magnetic field. In the high-beta regime, where β > 1 (β is the ratio of plasma-beam energy density to magnetic field energy density), beam magnetization occurs on a time scale orders of magnitude faster than the classical Spitzer time scale. Recent studies of fast magnetization suggest that transport processes in large ion gyroradius beams, γ/ρ[sub i] < 1, are dominated by ion motion rather than electron motion as previously understood for small gyroradius beams, γ/ρ[sub i] > 1, where y and ρ[sub i] are the beam transverse width and ion gyroradius, respectively. Although quantitative aspects of the small gyroradius propagation physics theory are still valid, most notably the E X B drift, much work remains to fully understand fast magnetic diffusion processes, beam-trapping mechanisms, and long-range propagation limits.


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