Time-Dependent Plasma Behavior Triggered by a Pulsed Electron Gun under Conditions of Beam-Plasma-Discharge
We have conducted a number of experiments intended to simulate spaceborne applications of energetic electron guns while exploring the “in situ” diagnostics of time-dependent beam-plasma behavior under pulsed electron gun conditions. The conditions include the beam-plasma-discharge (BPD) and the BPD afterglow that exists after gun-pulse termination. With electron gun characteristics set at (Ig, Vg, Ton /Toff) = (34 ma, 1.9 keV, 80 ms/270 ms) and a superimposed magnetic field at 1.5 gauss, the results show that: (i) There is a three order-of-magnitude increase in plasma density within 5 ms of gun turn-on; (ii) During the pulse-ON time a quasi-steady-state BPD is maintained with characteristics identical to dc-BPD conditions; (iii) Plasma losses appear to be dominated by Bohm-like diffusion processes; and finally (iv) The afterglow can be characterized by an isodensity radial profile that decays with a 36 msec time constant and cools at a 3.8(103) °K/sec rate.
KeywordsRadial Diffusion Langmuir Probe Electron Density Profile Beam Plasma Plasma Loss
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