Resonant circuit oscillations in travelling-wave tubes

Stability remains one of the most difficult problems in the design of high power travelling-wave tubes. Stability problems are also encountered in the design of low power tubes, but it is usually possible to predict the instabilities and obtain a stable design without seriously compromising gain and efficiency. However, in high power tube designs, instability can result in a limited active circuit length, thereby limiting each individual circuit gain to a value seriously affecting tube efficiency [1]. Obviously, the stability factor can limit the number of applications for high power travelling-wave tubes.