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Details a calculation on spontaneous radiation emitted by an electron beam passing through a continuously rotating quadrupole magnetic undulator. Information on the use of free-electron laser; Equations of motion; Characteristics of the radiation spectrum.

Presents a study which reduced the free-electron-laser (FEL) equations to a set of one-dimensional, normalized equations that allow a universal dimensional analysis. Performance characteristics of specific high-gain FEL; Estimates for the efficiency enhancement achieved with a tapered section; Design of high-gain millimeter-wave FEL amplifier using a superconducting short-period wiggler and sheet electron beam.

Presents procedures and quantitative analyses for obtaining and evaluating experimental short-period-wiggler free-electron lasers (FEL) oscillators that have been optimized with respect to efficiency. Applications for candidate sources of high-power, tunable, coherent radiation; Equilibrium operating point for the FEL oscillator; Effects of beam axial energy spread on the FEL interaction efficiency.

The spectral characteristics of a continuous beam free electron laser are studied both numerically and analytically. The average spectral width and the probability distribution of mode amplitudes determined from nonlinear numerical simulations are found to agree with a simple theory based on the linear growth of each mode in the presence of a white noise source. Included in the numerical simulation model is the time dependence of the beam energy and its effect on the spontaneous emission rate. Based on this model predictions of the frequency of observing a single dominant mode in the recent University of California at Santa Barbara experiments [FEL ’89, 11th International Conference on Free Electron Lasers, Conference Digest (IEEE), New York, 1989), Paper p. 2.19] are made. The predicted frequency is somewhat lower than observed. However, other features of the simulations do agree with experimental results. [ABSTRACT FROM AUTHOR]

The stability of single-mode operation of free electron laser (FEL) oscillators is investigated. Two models of an untapered FEL oscillator are considered. The first model is called the klystron model. In the klystron model the FEL interaction occurs at two points: a prebunching point and an energy extraction point. In this model the nonlinear electron dynamics are solvable exactly, leading to a complex delay equation for the wave fields. The stability of single-mode operation can then be determined easily as a function of a single-pass gain, energy mismatch-frequency, and the difference between the group velocity of the radiation and the beam velocity. The second, more realistic model has a distributed interaction region of finite length: Stability of single-mode operation in this device must be determined numerically. The results of the models in the low gain regime are compared and the parameter regimes where stable single-mode operation is possible are determined. It is found that the time to reach a single-mode state can be extremely long. [ABSTRACT FROM AUTHOR]

Using a normalized set of nonlinear equations, which describe a free-electron laser (FEL) oscillator, the efficiency of energy extraction from the electron beam to the radiation can be optimized. The optimum values of this efficiency are presented for (a) an untapered and (b) a tapered wiggler FEL oscillator. [ABSTRACT FROM AUTHOR]

A new rotating quadrupole wiggler configuration for free-electron lasers is proposed. The stability analyses of the particle trajectories in a continuously rotating quadrupole magnetic field and self-fields of a solid beam are performed. The resulting orbit equations are solved exactly and it is shown that high-current beams can be confined. To analyze the potential of this wiggler for free-electron lasers, a set of nonlinear orbit equations is derived which averages over the fast time variation in both the wiggler and radiation fields. By integrating these equations, the linearized single particle gain of the free-electron laser is calculated. It is shown that, at comparable wiggler strengths, the rotating quadrupole wiggler and conventional wiggler give similar gains. [ABSTRACT FROM AUTHOR]

The nonlinear theory of optical guiding in a free electron laser amplifier is developed for the case in which the axial and radial dependence of the fluctuating current in the electron beam can be separated. Such a separation can be motivated if either the betatron wavelength is shorter than other lengths of interest (synchrotron wavelength, vacuum Rayleigh length) or if the radiation waist exceeds the beam radius. In such cases, assuming a Gaussian profile for the electron beam density enables the wave equation to be solved exactly and the radiation field experienced by the particles to be expressed as a one-dimensional convolution of the current source. Analytical and numerical calculations of the effect of diffraction on the gain and nonlinear saturation of a free electron laser amplifier are presented. The constraints imposed by diffraction on efficiency enhancement by tapering are examined. [ABSTRACT FROM AUTHOR]

Proposes a wiggler-focused, sheet beam free electron laser amplifier utilizing a short-period wiggler magnet as a millimeter-wave source for current profile modification and/or electron cyclotron resonance heating of tokamak plasmas. Operating conditions of the amplifier; Range of electron beam energy.

Examines the millimeter-wave amplification in a sheet beam free electron laser. Gain observed in a 54 centimeter wiggler; Wave energy absorption at off-resonance beam energy; Potential of the device configuration for producing equally high output power at low voltage.