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Experimental studies of coaxial plasma gun current

Thesis/Dissertation ·
OSTI ID:6909626

In this investigation of a coaxial plasma gun, plasma sheath currents and related behavior are examined. Plasma behavior in the gun affects gun characteristics. Plasma gun applications are determined by the plasma behavior. The AFWL PUFF capacitor bank (72 {mu}F, 29 nH, 120 kV) drives the plasma gun using a deuterium fill gas. The gas breakdown site is isolated from the dielectric/vacuum interface in the AFWL system. Two gas values deliver gas in the system. The first delivers gas from the gun breech and the second optional valve delivers gas to the gun muzzle. Currents and voltages are measured by Rogowski coils, B probes and capacitive voltage probes. A O-D slug model is used to predict the current, inductance, gun voltage and plasma sheath velocity. The slug model assumes the sheath transits the gun with all mass in the sheath. In the snowplow mode, the plasma sheath is thin with a sharp current rise and drop. Our system operated in a transition mode between the snowplow and deflagration modes with early snowplow behavior and late deflagration behavior. Neutrons are produced in a plasma pinch at the gun muzzle, indicating snowplow behavior. The slug theory models overall gun behavior to experimental accuracy. Experimental results are compared to four theories for plasma sheath velocities: the Alfven collisionally limited model, the Rosenbluth model, the Fishbine saturated model and a single particle drift model. Experimental velocities vary from 10{sup 5} to 10{sup 6} m/s. Only the single particle drift and the slug model calculations are of the right magnitude (8 {times} 10{sup 5} m/s). The Fishbine and the Rosenbluth models predict slower velocities (2 {times} 10{sup 5} m/s). The Alfven model is not applicable to this system.

Research Organization:
New Mexico Univ., Albuquerque, NM (USA)
OSTI ID:
6909626
Country of Publication:
United States
Language:
English