Reflexions and gain ripple in TWT´s

The presence of the electron beam in a TWT introduces additional internal reflexions that are not present in the cold tube, at the output, at the input, and at the attenuator. These additional reflexions, that we denote "electronic reflexions,"increase the gain ripple. The electronic reflexions are hard to measure and therefore have to be calculated. In the present paper, equations are derived for them as functions of Pierce\´s TWT parameters. A conclusion is that the electronic reflexions often exceed the cold reflexions that can be obtained in practice. The electronic reflexions in TWT\´s with a backward fundamental coupled-cavity structure are almost an order of magnitude larger than those in helix TWT\´s.