Beam transmission in a high-power collective free-electron laser
- Naval Research Laboratory, Washington, D.C. 20375 (United States)
A recent free-electron laser amplifier experiment conducted at the Massachusetts Institute of Technology [M. E. Conde and G. Bekefi, Phys. Rev. Lett. [bold 67], 3082 (1991)] has demonstrated high-power operation without recourse to a tapered wiggler field. The experimental configuration consisted in the propagation of an intense electron beam (750 keV/300 A with a nominal axial energy spread of 1.5%) through a cylindrical waveguide in the presence of both a helical wiggler ([ital B][sub [ital w]][le]1.8 kG and [lambda][sub [ital w]]=3.18 cm) and an axial guide magnetic field ([ital B][sub 0][le]12 kG). The experiment operated with the axial guide field oriented both parallel and antiparallel to the direction of the wiggler field, and the maximum efficiency was obtained for the antiparallel (i.e., reversed-field) configuration. The reversed-field case demonstrated an output power of 61 MW at 33.39 GHz for an efficiency of approximately 27%. The performance in the more usual parallel alignment of the fields was much less and peak power levels of only about 4 MW were obtained for both the weak (group I) and strong (group II) field regimes of the axial guide field. A detailed analytical characterization of this experiment has been presented in a previous work [H. P. Freund and A. K. Ganguly, IEEE Trans. Plasma Sci. [bold PS]-[bold 20], 245 (1992)] in which substantial agreement was found between the theory and the experiment for the reversed-field configuration. However, some discrepancies existed for the group I and II cases, and it was conjectured that some problem with beam transport existed for these configurations which led to an increased beam energy spread. In this paper, the question of beam transport in this experiment is analyzed. It is shown that beam transport is not a problem for the reversed-field configuration.
- OSTI ID:
- 5649738
- Journal Information:
- Physics of Fluids B; (United States), Vol. 5:6; ISSN 0899-8221
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
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FREE ELECTRON LASERS
BEAM TRANSPORT
ELECTRON BEAMS
POWER
TRANSMISSION
WAVEGUIDES
WIGGLER MAGNETS
BEAMS
ELECTRICAL EQUIPMENT
ELECTROMAGNETS
EQUIPMENT
LASERS
LEPTON BEAMS
MAGNETS
PARTICLE BEAMS
426002* - Engineering- Lasers & Masers- (1990-)
661220 - Particle Beam Production & Handling
Targets- (1992-)