Acoustic resonances in cylindrical high-pressure arc discharges

Abstract

Acoustic resonances were observed in high-pressure (600 Torr) sodium-mercury-xenon discharges operated with ac input at power frequencies of 2–120 kHz. Three sizes of cylindrical sapphire arc tubes were operated at constant average powers of 400, 250, and 150 W, respectively. The observed resonance frequencies and arc shapes agree well with a simple analysis of standing pressure waves in cylinders. The results indicate that transverse resonances effectively average the gas temperature across the arc, while longitudinal resonances mainly involve the hot core of the discharge.