Coaxial Plasmoid Source of Small Aspect Ratio

An annular source is described which approximates a one-dimensional geometry. Characteristic behavior is given, primarily for one set of operating parameters. A fast-acting valve injects 0.3 cc STP hydrogen, and capacitor firing is timed to permit operation in the ``slug'' mode. Photomultiplier data indicate a luminous front acceleration (for 40 cm) to a muzzle velocity of 103 cm/μsec; position probes yield 74 cm/μsec. The data appear to verify a hydromagnetic acceleration model, based on analog computation for a 0.06-μg slug (which is more than half the gas available in the annulus). The theoretically expected momentum is 6.2 dyn-sec; experiment yields 11.4 dyn-sec. Tentative number density and electron temperature are 3 × 1014/cc and 3.6 eV, respectively, the latter obtained by a double Langmuir probe. The discussion includes efficiency considerations and a brief examination of the ion and electron collisional and gyromagnetic parameters.