Paul A. Bernhardt, Plasma Physics Division, Naval Research Laboratory

Title: Plasma Globes for Compact Antennas, Illumination, and Holiday Ornaments  (Video)

Abstract: A new technique has been developed to produce glowing balls of plasma that float in the center of a vacuum chamber.  These plasma globes are sustained by external source microwaves that are amplified by more than one-hundred inside a spherical porous cavity resonator (SPCR).  Ionization of the neutral atmosphere occurs at the center of the spherical resonator where large electric fields accelerate electrons above the breakdown threshold of the gas.  Applications of the plasma cloud generation technology includes (1) production of a compact radiator for frequencies that produce a relative dielectric constant of -2 inside a uniform plasma sphere, (2) construction of an intense short pulse flash lamp for sterilization and stop motion, and (3) commercial decorations for the holiday season.  The production of the plasma globes is described by a three-dimensional model that couples Maxwell’s Equations in spherical geometry with time dependent equations with diffusive transport, and electron-ion recombination.  The theory shows that the high-Q resonator is detuned as soon as the internal plasma ball appears.  Maximum plasma density is achieved with a broad spectrum microwave source or by retuning the frequency of a narrowband source.  The maximum plasma density achievable using this technique is 31/2 Critical Density of the source pump frequency.