Three-Dimensional Simulation of Free Electron Laser with Prebunching and Efficiency Enhancement

Authors: M. Chitsazi, B. Maraghechi, M. H. Rouhani

Abstract:

Three-dimensional simulation of harmonic up generation in free electron laser amplifier operating simultaneously with a cold and relativistic electron beam is presented in steady-state regime where the slippage of the electromagnetic wave with respect to the electron beam is ignored. By using slowly varying envelope approximation and applying the source-dependent expansion to wave equations, electromagnetic fields are represented in terms of the Hermit Gaussian modes which are well suited for the planar wiggler configuration. The electron dynamics is described by the fully threedimensional Lorentz force equation in presence of the realistic planar magnetostatic wiggler and electromagnetic fields. A set of coupled nonlinear first-order differential equations is derived and solved numerically. The fundamental and third harmonic radiation of the beam is considered. In addition to uniform beam, prebunched electron beam has also been studied. For this effect of sinusoidal distribution of entry times for the electron beam on the evolution of radiation is compared with uniform distribution. It is shown that prebunching reduces the saturation length substantially. For efficiency enhancement the wiggler is set to decrease linearly when the radiation of the third harmonic saturates. The optimum starting point of tapering and the slope of radiation in the amplitude of wiggler are found by successive run of the code.

Keywords: Free electron laser, Prebunching, Undulator, Wiggler.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1331095

References:

[1] H. P. Freund, D. Douglas, and P. G. O'Shea, "Multiple-Beam Free- Electron Lasers," Nucl. Instrum. Methods A, vol. 507, pp. 373-377, July 2003.
[2] H. P. Freund, S. G. Biedron, S. V. Milton, "Nonlinear Harmonic Generation in Free-Electron Lasers," IEEE J. Quantum Electron, vol. 36, pp. 275-280, March 2000
[3] G. R. Neil, H. P. Freund, "Nonlinear Harmonic Generation in Distributed Optical Klystrons" Nucl. Instr. and Meth. A, vol. 475, pp. 373-376. December 2001.
[4] S. G. Biedron, H. P. Freund, S. V. Milton, L.-H. Yu, X. J. Wang, "Modular Approach to Achieving the Next-Generation X-Ray Light Source," Nucl. Instr. and Meth. A, vol. 475, pp. 401-406, December 2001.
[5] M. H. Rouhani and B. Maraghechi, and H. Saberi, " Efficiency Enhancement of a Two-Beam Free-Electron Laser," Phys. Plasmas, vol. 16, 123105. December 2009.
[6] M. H. Rouhani and B. Maraghechi, "Efficiency Enhancement in Seeded and Self-Amplified Spontaneous Emission Free-Electron Laser," Physics of plasma. vol. 16, pp. 093110, 2009.
[7] H. P. Freund W. H. Miner, Jr. "Efficiency Enhancement in Seeded and Self-Amplified Spontaneous Emission Free-Electron Laser by Means of a Tapered Wiggler," j. Appl. Phys. Vol. 105, pp. 113106 - 113106-6, 2009.