Relativistic bulk-wave source with electronic mode selection

An electronic technique for selecting specific modes in multimode microwave sources with two periodic structures with different periods is described. A hollow electron beam is focused on a circular, oversized waveguide to excite an electromagnetic field. Two periodic, slow-moving wave structures on the guide are separated by a drift tube. The beam is synchronized to the minus first harmonic of the backward wave of one of the bulk modes to modulate the other structure. The field of the first mode is transferred into energy for the second, resulting in a forward traveling release of microwave power. Applications of the device in a beam accelerator are discussed.