Spectral measurements of gyrotron oscillator with ferroelectric electron gun

Since the discovery of the ferroelectric electron-emission effect, its implementation in microwave tubes has been impeded by various reasons and in particular by its relatively wide energy spread. Recently, a 1.5 kW microwave output from a gyrotron based on repetitive ferroelectric electron gun has been reported. This letter presents measurements of the spectral variations of the gyrotron output, and relates them to the electron-gun energy spread and to other inherent line-widening causes, such as the pulse length. The result shows that the contribution of the electron energy spread to the spectral content is not significantly larger than the other causes of line broadening.