BEAM PROBE MAPPING OF RAPIDLY FLUCTUATING PLASMA DENSITY IN AN ENERGETIC ARC.
Rept. no. 4 (Final), 1 Dec 67-30 Nov 68,
MOBIL RESEARCH AND DEVELOPMENT CORP PRINCETON N J CENTRAL RESEARCH DIV LAB
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The rapidly fluctuating density in an energetic arc plasma was mapped with good spatial and temporal resolution by probing the plasma with an energetic H2 molecular ion beam. The H atomic ion current produced by collisional dissociation of the H2 ions was sampled in synchronization with a coherent oscillation in the arc plasma to produce stroboscopic maps at six different phases. Both the total density of the arc and the density perturbation of the oscillation, which was an m 1 azimuthal wave propagating about an off center axis, were measured. Conventional assumptions, such as cylindrical symmetry and the concentricity of the density and the density perturbation, which are widely used to interpret less detailed measurements, are shown to be invalid for this helium arc and are probably invalid for similar systems. Three generalizations of the beam probing technique are also discussed in the report 1 A low energy heavy ion beam for probing both plasma density and space potential 2 A fast multi-channel recording and data handling system for making real-time maps 3 The density distribution in the outlet of a neutral gas jet. Author
- Plasma Physics and Magnetohydrodynamics