Superradiance of extended electron bunches
IAP has proposed to use induced radiation of spatially localized electron ensembles (bunches), which are either magnetically trapped (V. V. Zheleznyakov, V. V. Kocharovsky, Vl. V. Kocharovsky), or moving in waveguide structures (N. S. Ginzburg, I. V. Zotova), as a way to generate ultrashort electromagnetic pulses. The use of such bunches can be regarded as the classical analogue of the Dicke superradiance known in quantum electronics, under which an ensemble of inverted atoms emits an electromagnetic pulse with its duration being short as compared with the relaxation times.
The superradiance effects served as the basis for the joint developments of IAP, the Institute of Electrophysics of the Ural Branch of RAS, and the Institute of High-Current Electronics of the Siberian Branch of RAS, which resulted in creation of a new class of high-power microwave generators with an ultrashort pulse duration (up to 0.3–1 ns). Superradiance (SR) related to the stimulated cyclotron, undulator, and Cherenkov mechanisms of radiation of extended electron bunches has been demonstrated, as well as SR arising in the process of induced scattering of a pumping wave.
The maximum SR power (with high stability and repeatability of the pulse shape) has been obtained for the Cherenkov interaction of a straight-moving electron bunch with the synchronous spatial harmonics of the backward wave in the periodic slowing-down system (the long-pulse version of a similar radiation mechanism is used in BWOs). Slippage of the radiation relative to the electron bunch can lead to a cumulative increase in the amplitude of the SR pulse due to its interaction with different electron fractions. In such situation, the peak power of the radiation can exceed the power of the electron beam.