Two magnetically insulated gas-puff diodes were tested. In one design the plasma source was a fast inductive coil; in the other a coaxial gun created the plasma. The plasma current density from both sources, as well as the accelerated beam from each, was comparable to the Child-Langmuir limit of ∼10 A/cm 2.

A gas-puff magnetically insulated ion diode is under development as a pulsed source of high-energy alpha particles for magnetic fusion experiments. The diode is patterned after the Cornell gas-puff diode [J. B. Greenly, M. Ueda, G. D. Rondeau, and D. A. Hammer, J. Appl. Phys. 63, 1872 (1988)], but with modifications to accomodate higher voltages (<1 MeV) and operation in helium. The diode is designed to yield current densities approaching 200 A/cm 2 one meter downstream from the source; in our first test of the new source, a helium beam was obtained.

The propagation of an intense neutralized ion beam (v∼5 × 10 8 cm/sec, n∼1010 cm-3) through a large insulated vacuum chamber is measured as a function of magnetic field strength and direction. When the beam propagates parallel to the applied field, beam divergence is reduced. When the beam propagates perpendicular to the applied field, the downstream beam density decreases with increasing field strength. When the beam velocity vector intersects the magnetic field at an oblique angle, beam propagation is determined primarily by the perpendicular component of the field. © 1992 American Institute of Physics.