Microwave Undulator Using a Helically Corrugated Waveguide

Abstract

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.Index Terms-microwave undulator, free electron laser, helically corrugated waveguide, traveling wave mode.

Beam dynamic study of a Ka-band microwave undulator and its potential drive sources

“…The backward wave exists in a cavity as a standing wave or a waveguide as a traveling wave. Therefore, the MU can be classified as a cavity-type or waveguide-type MU 21 – 23 . For the waveguide-type MU, in the ideal case, the entire EM wave energy is confined within the region of the beam aperture in radius.…”

“…The fundamental differences between a permanent magnet undulator and a microwave undulator have been studied and presented in Refs. 17 , 23 . In the cavity-type MU, the relativistic electrons see both electric and magnetic fields.…”

Low-Loss Transmission Line for a 3.4-kW, 93-GHz Gyro-Traveling-Wave Amplifier

“…2). At the intersection point, where the Bragg resonance conditions are satisfied, the two modes have strong coupling and can convert the energy of the input mode to the output mode [20]. Theoretically, this kind of mode converter is able to achieve mode coupling between any two modes.…”

Radio-Frequency Undulators, Cyclotron Auto Resonance Maser and Free Electron Lasers

“…The scientific literature on the subject of RF undulators has significantly grown in the past and a partial list can be found in [19][20][21][22][23][24][25][26][27][28][29].…”