A free-electron laser consists of an electron beam propagating through a periodic magnetic field. Today such lasers are used for research in materials science, chemical technology, biophysical science, medical applications, surface studies, and solid-state physics. Free-electron lasers with higher average power and shorter wavelengths are under development. Future applications range from industrial processing of materials to light sources for soft and hard x-rays.
The emission at the second harmonic (2ωe) of the plasma frequency from self‐consistent Langmuir solitons is calculated. The theory predicts, in a natural way, the observed transition from the region where the intensity is linearly proportional to the electron flux to the region where the radio intensity is proportional to the square of the electron flux. A detailed comparison of the radiation observed at (2ωe), for the burst of 31 March 1976, 18:10 UT with the one expected on the assumption of radiation from solitons, using the correlated in situ measurements of the electric fields at ωe and their spatial structure provides strong evidence that, for the first time, Langmuir solitons have been observed in space.
SPARC (acronym of ‘‘Sorgente Pulsata ed Amplificata di Radiazione Coerente’’, i.e. Pulsed and\ud
Amplified Source of Coherent Radiation) is a single pass free-electron laser designed to obtain high gain\ud
amplification at a radiation wavelength of 500 nm. Self-amplified spontaneous emission has been\ud
observed driving the amplifier with the high-brightness beam of the SPARC linac. We report measurements\ud
of energy, spectra, and exponential gain. Experimental results are compared with simulations from\ud
several numerical codes
Recently, a 3D, polychromatic, nonlinear simulation code was developed to study the growth of nonlinear harmonics in self-amplified spontaneous emission (SASE) freeelectron lasers (FELs). The simulation was applied to the parameters for each stage of the Advanced Photon Source (APS) SASE FEL, intended for operation in the visible, UV, and short UV wavelength regimes, respectively, to study the presence of nonlinear harmonic generation. Significant nonlinear harmonic growth is seen. Here, a discussion of the code development, the APS SASE FEL, the simulations and results, and, finally, the proposed experimental procedure for verification of such nonlinear harmonic generation at the APS SASE FEL will be given.
The nonlinear evolution of the Cerenkov maser amplifier is investigated numerically for a configuration that consists of an energetic electron beam propagating through a dielectric-lined cylindrical waveguide. An axial guide magnetic field is included in the formulation in order to improve beam confinement. A set of coupled nonlinear differential equations is derived in three dimensions that governs the evolution of both the electromagnetic field and the trajectories of an ensemble of electrons. The system is assumed to be azimuthally symmetric, and the electromagnetic field is represented as a superposition of the TM0n modes of the vacuum waveguide. The initial conditions are chosen to model the simultaneous injection of either a solid or annular electron beam, and an electromagnetic wave of arbitrary input power. Thermal effects are treated under the assumption that the beam is initially monoenergetic but exhibits a pitch angle spread; however, the subsequent evolution of the beam is treated in a self-consistent manner. This class of distribution is appropriate to the treatment of diode-produced beams and describes a beam with an initial axial energy spread. This is the crucial determinant in the efficiency, since saturation occurs by means of an axial bunching mechanism that results in the phase trapping of the beam. The specific parameters used in the numerical analysis correspond to experiments conducted at Dartmouth College [J. Appl. Phys. 58, 627 (1985)], and good agreement is found between theory and experiment.
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