Ionic Oscillations in the Glow Discharge

In an effort to correlate Whiddington's work on moving striae and Appleton's work on ionic osciallations from a striated discharge, it was found that the ionic oscillation phenomenon was sufficiently involved to warrant a detailed study. The discharge tube was of the hot cathode type, 3 cm in diameter and 26 cm long. The oscillations were detected in three ways: first, by means of curved plates on the tube which were connected in parallel with the tuning condenser of the receiver; second, by direct inductive "pick-up" from the tube itself; third, by inductive "pick-up" from a coil in series with the tube. By these methods frequencies from 15×${10}^4$ to a few hundred cycles were obtained, the higher frequencies being detected on an auto-dyne receiver, the lower frequencies on a straight low-frequency amplifer. Characteristic curves obtained show an increase of frequency with filament current, an increase of frequency with anode potential and a decrease with pressure except at the lower pressures where the frequency increases, passing through a maximum. With a varying pressure and without plates on the tube, oscillations do not occur when there are sharply defined striae but begin just as striae begin to diffuse, decreasing in frequency and becoming audible when a uniform glow fills the tube.