Microwave undulator using a helically corrugated waveguide

Microwave undulators (MU) can be an alternative to the permanent magnet undulators in a free electron laser (FEL). MUs normally employ a cavity-type structure that supports the standing wave to boost the electromagnetic field strength. In this paper, a waveguide-type MU based on a helically corrugated waveguide (HCW) that supports a traveling wave is studied. The use of the HCW allows partial conversion of a traveling wave mode into a backward traveling wave mode, hence increasing the effective interaction length. When operating with a TE11 mode at 30.3 GHz, the MU was predicted to realize a field strength of ~0.3 T and an undulator period of 4.95 mm when driven by 1 GW of microwave power. The support of the STFC UK (Cockcroft Institute Core GrantR160525-1) is gratefully acknowledged. This work is supported by European Union (EU) Horizon 2020 Project “CompactLight” 2017-2021. “CompactLight” grant code: 777431-XLS. Published data 26 November 2018, under Self-archiving / 'green' OA