The Cerenkov Free-Electron Laser
Abstract
In the Cerenkov free-electron laser experiments, dielectric-loaded quasi-optic resonators were used to couple the electron beam to the electromagnetic field. Three types of electron beam generators were employed: a pulse-transformer-based modulator (which operates in the 50-250 KV range), a Marx generator (which operated in the 500 kv - 1.1 MV range), and a circular RF accelerator (microtron) operating at 5 Mev. The pulse-transformer-based system was used primarily for mm-wavelength experiments. On the fundamental branch (TM01) of a cylindrical shell-loaded guide, operation between 30 and 150 GHz was obtained. A single resonator will typically tune over a 20-30 percent range and the electronic efficiency peaked near the lower end of the tuning curve for a fixed resonator geometry. The magnitude of the efficiency at wavelengths near 3 mm was typically 4-6%. Operation on TM02 at lower efficiency (0.1-1%) was used to extend the operating range above 300 Ghz (350 Ghz typical). However, efficiencies were obtained on occasion. Overall, the moderate-beam-voltage driven C-FEL is a simple, robust source of mm- and near-mm-wavelength radiation. Its principle disadvantage is the requirement for very careful beam focussing since any substantial charging of the dielectric liner will disrupt the beam flow.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 22, 1988
- Accession Number
- ADA203531
Entities
People
- John E. Walsh
Organizations
- Dartmouth College