Experimental Studies of the Penetration of a Plasma Stream into a Transverse Magnetic Field

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Abstract
The interaction of a dense (n ≃ 3 × 1013 cm−3), fast (v ≃ 4 × 107 cm/sec) plasma stream with a transverse magnetic field is studied experimentally by injecting a plasma from a coaxial gun perpendicular to the magnetic field of a pair of mirror coils. The experiments show that the stream from such a gun can penetrate magnetic fields up to ∼9 kG. A rapid field‐plasma intermixing takes place and the injected stream crosses the magnetic field by electrically polarizing and producing an E × B drift. It was found that the forward motion of the stream can be stopped by draining the polarization charge by current flow along field lines to a shorting conductor located outside a magnetic mirror. Measurements of stream thickness normal to the magnetic field and the effectiveness of the depolarizing conductors have been made as a function of the strength of the transverse field. The exclusion of the plasma from high magnetic fields, and the variation of stream width with magnetic field intensity are due to plasma polarization effects rather than plasma diamagnetism. Observations on high energy electrons > 200 keV which are produced during the experiment are discussed.