Nonlinear Analysis of Efficiency Enhancement in Ubitron/Free-Electron Laser Amplifiers.
Abstract
A technique for efficiency enhancement in Ubitron/Free-Electron Laser amplifiers is analyzed which makes use of both tapered wiggler and axial guide magnetic fields. A set of model equations is derived which describes the coupling between an ensemble of electrons and the radiation field. The analysis is fully three-dimensional, and treats the propagation of an electron beam of finite cross-sectional area through a loss-free cylindrical waveguide in the presence of a helically symmetric wiggler field and an axial guide magnetic field. The model equations are solved numerically, and substantial enhancements in the interaction efficiency are found for a variety of choices of the model parameters. The efficiency enhancement is observed to be a sensitive function of both the degree of taper in the wiggler and axial magnetic fields as well as the point at which the taper is begun. In order to illustrate the physical mechanism underlying the efficiency enhancement, a modified pendulum equation which describes the interaction is derived from the orbit equations under a set of idealized assumptions, and used to construct a small-signal theory of the efficiency enhancement.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 21, 1986
- Accession Number
- ADA163619
Entities
People
- A. K. Ganguly
- H. P. Freund
Organizations
- United States Naval Research Laboratory