ABSTRACT
Klystrons have two distinguishing features. First, the microwave-generating interactions in these devices take place in resonant cavities at discrete locations along the beam. Second, the drift tube connecting the cavities is designed so that electromagnetic wave propagation at the operating frequency is cut off between the cavities; without electromagnetic coupling between cavities, they are coupled only by the bunched beam, which drifts from one cavity to the next. This latter feature of these devices, the lack of feedback between cavities, makes them perhaps the best-suited of HPM devices to operate as amplifiers.*
To guide the beam along the drift tube, an axial magnetic guide field is applied, so that klystrons and reltrons (in those instances where a magnetic field is applied) are O-type devices. By contrast, in other O-type devices, such as the Cerenkov sources, free-electron lasers, or gyro-devices, microwaves are generated by beam-wave resonances that transfer beam energy to a wave over an extended interaction space or in a series of electromagnetically coupled cavities. The attractions of klystrons are their high power and efficiency, potentially wide bandwidth, and phase and amplitude stability.
