A self-confined high-power Cherenkov oscillator operating at high-frequency

We present initial predictions for the performance of a novel microwave source, in form of a high-power Cherenkov oscillator, that operates with no externally applied magnetic insulation of the propagating electron beam; i.e. the source relies solely on the self-fields of the electron beam for propagation. The result being that the conversion efficiency - that is, the energy extracted from the electron beam to the growing electromagnetic wave - is closely linked to the overall energy efficiency of the source.
Appearing similar in construction to the conventional, magnetically insulated, relativistic Backward-Wave Oscillator (BWO), the source has been termed a Self-Insulating BWO (SIBWO). Conversion efficiencies in excess of 30% have been predicted in simulation, using CST Studio Suite, corresponding to output powers in excess of 300MW from a 500keV, 2kA electron beam, operating in the expected TM01 mode at ~9.4GHz.
As the operation of the source is intrinsically tied to the quality of the propagated electron beam, a tolerance study has been performed, varying the critical beam parameters over the range expected in experiments. The results show the efficiency remains better than ∼20%, even when operating with a relatively poor-quality beam (for e.g. showing large angular spread). Examination of the effect of variation in the mean beam energy, over an extended range of 400 - 600keV, showed the efficiency of the source remaining above 20%, across this range.