A periodically focused backward-wave oscillator

The application of some new periodic focusing techniques to the backward-wave oscillator is discussed. An oscillator utilizing a hollow electron beam was constructed at S-band. A periodic electrostatic focusing method was used with considerable success, and an octave tuning range was obtained. A periodic magnetostatic focusing method was attempted with less encouraging results. Some interesting effects were observed when the periodic focusing techniques were applied and some of these are described.