Spectroscopic measurements of a toroidal air plasma

A multi-millisecond duration, exploding wire air plasma with electron density of at least 10¹⁴-10¹⁵ /cm³ has been developed. Confining the radial expansion of an exploding wire discharge has resulted in interesting hydrodynamic effects, producing a toroidal air plasma, or TAP. This plasma has been characterized with a diagnostic suite, including an Acton Research Corporation SpectraPro-300i with a 300 g/mm grating blazed at 500 nm, a quartz-silica fiber optic of 400 μm diameter, and the Princeton Instruments ICCD-MAX intensified CCD. Wavelength calibrations were performed in WINSPEC software against known wavelengths from a mercury-argon pen lamp. Each spectrum was calibrated against data from two spectral irradiance lamps: a 30 Watt deuterium lamp and a 200 Watt quartz tungsten halogen lamp. Spectrographic measurements have been taken to obtain a black body curve of TAP from 200 to 800 nm. The peak emission of TAP was found to be between 350 and 400 nm. These results presented suggest a black body temperature of the TAP of 7733 K. The results of the measurements and the implications of the spectra are reported, along with high speed videos which indicate that the plasma is self-confining and has a long lifetime in air.