Generation of Cherenkov superradiance pulses with a peak power exceeding the power of the driving short electron beam

Theoretical investigation of a short electron beam (extended bunch) interaction with a backward wave propagating in a slow wave structure demonstrates the possibility of producing ultrashort superradiance pulses with a peak power which exceeds the power of the driving beam (conversion factor $K>$1). It is shown that a nonuniform slow wave structure with optimized profile is beneficial in order to increase the conversion factor. The results of theoretical analysis are confirmed by the experiments. At X band using the SINUS-150 accelerator (40.3em0exns, 3300.3em0exkV, 2.60.3em0exkA) 0.6--0.80.3em0exns superradiance pulses with a peak power of 1.20.3em0exGW and a conversion factor of 1.5 were obtained. Similar experiments at Ka-band based on the RADAN-303 accelerator (10.3em0exns, 2900.3em0exkV, 2.50.3em0exkA) demonstrated production of the superradiance (SR) pulse with duration 2000.3em0exps and peak power about 10.3em0exGW (conversion factor of 1.4).