Enhancement-limit of Smith–Purcell radiation with self-bunched keV-order electron beam

Abstract

We studied enhanced Smith–Purcell (SP) radiation produced by a self-bunched keV-order electron beam based on a W-band surface-wave oscillator. The self-bunched beam is generated in the process of the beam interaction with the surface-wave mode. The bunched beam contains the second harmonic of the surface wave that enhances the SP radiation. The observed radiation shows that the enhancement is limited when the interaction transitions from the Compton regime to the Raman regime.

Experimental study on performance change in F-band surface-wave oscillator due to slow-wave structure length

“…In the case of the 80-period, the power is decreasing when the beam current exceeds 100 A, as reported in Ref. 24. On the other hand, in the case of the 120-period and the 200-period, the power is increasing even when the beam current exceeds 100 A.…”

“…This comparison shows that the current dependence of the power changes with the SWS length above 100 A. In the case of the 80-period, the power is decreasing when the beam current exceeds 100 A, as reported in Ref 24…”

“…When the global instability is formed in the finiteness of SWS like the 80-period case in Ref. 24, the spatial growth rate may be a more practical and critical measure of the instabilities than the temporal growth rate. In this case, the BWO oscillation is caused by global instability and is ruled by the spatial growth rate.…”