Propagation of neutralized plasma beams

Beams of charge- and current-neutralized plasma will cross a transverse-magnetic field by a combination of collective-plasma processes. These processes were studied for a high -to-low beta (β ≡ plasma energy density/magnetic field energy density) hydrogen-plasma beam injected into a vacuum transverse magnetic field with nominal parameters: T
_i
≈ 1 eV, T
_e
≈ 5 eV, n ≤ 10
¹⁴
cm
^-3
, v
_i
≤ 9 × 10
⁶
cm/s, t
_pulse
<; 60; 70 μs, B
_z
≤ 300 G. Plasma characteristics were measured for a wide beam, a/ρ
_i
≤ 35, and a downstream distance, x ≤ 300 ρ
_i
, where a is the beam radius, x is the downstream distance, and ρ
_i
is the ion gyroradius. A brief state of initial diamagnetic propagation is observed, followed by a rapid transition to E×B propagation. E×B propagation is accompanied by beam compression transverse to B. with as much as a factor of four increase in density and a slight drift of the beam in the ion Lorentz force direction. As the magnetic field increases, the observed magnetization time decreases from that calculated using classical Spitzer conductivity, approaching an order of magnitude. This rapid magnetization can be accounted for using classical Hall conductivity, rather than invoking anomalous processes or instabilities to calculate the magnetization time.