Instability in a cold cathode reflex discharge

The behaviour of a low-pressure cold-cathode reflex discharge has been studied to determine the nature of the instability which appears in the presence of a d.c. magnetic field. It was found that electric fields at a frequency of 5 Mc/s were generated by the plasma and were of intensity sufficient to modify the plasma and so stop these oscillations. The plasma then relaxed to a state where the instability reappeared. It was also determined that the effect of the radial d.c. electric field on the instability was negligible. If one assumes that an adequate model of the reflex discharge is that of a cold plasma column filled with a fast beam of primary (ionizing) electrons, it can be shown that the solution of the dispersion relationship shows growing waves for the measured plasma parameters.