ELECTROMAGNETIC PROPERTIES OF OPEN AND CLOSED OVERMODED SLOW-WAVE RESONATORS FOR INTERACTION WITH RELATIVISTIC ELECTRON-BEAMS

Specific slow wave structures are needed in order to produce coherent Cherenkov radiation in overmoded relativistic generators. The electrom agnetic characteristics of such slow wave, resonant, finite length str uctures commonly used in relativistic backward wave oscillators have b een studied both experimentally and theoretically. In experiments, per turbation techniques were used to study both the fundamental and highe r order symmetric transverse magnetic (TM) modes. Finite length effect s lead to end reflections and quantization of the wave number. The eff ects of end reflections in open slow wave structures were found from t he spectral broadening of the discrete resonances of the different axi al modes. The measured axial and radial field distributions are in exc ellent agreement with the results of a 2-D code developed for the calc ulation of the fields in these structures.