Observations of Acoustic Waves Generated in a Neon Glow Discharge

Abstract

Using two calibrated condenser microphones located within a discharge tube, measurements were made of the sounds generated by phenomena associated with moving striations in a dc discharge in neon at pressures of several Torr and at currents ranging from 5 to 100 mA, thus confirming observations reported in 1965 by W. A. Saxton. Acoustic pressures up to several microbars in amplitude existed at the end of the tube during naturally occurring oscillations. Oscillation frequencies from a few hundred to over 1000 were common. Based on phase measurements at different frequencies, it is concluded that the sounds are generated by fluctuations in heating processes at or very near the cathode owing to oscillations in the tube current. It appeared that, in this apparatus, the sounds generated during naturally occurring oscillations are secondary effects and do not appreciably affect the striation phenomenon. External modulation of the electrode potentials increases the sound pressures and appears to affect the striations. Experimental data are presented and discussed. [Work supported by the U. Office of Naval Research.]