| Autor: |
M. H. Rouhani, B. Maraghechi |
| Jazyk: |
angličtina |
| Rok vydání: |
2010 |
| Předmět: |
|
| Zdroj: |
Physical Review Special Topics. Accelerators and Beams, Vol 13, Iss 8, p 080706 (2010) |
| Druh dokumentu: |
article |
| ISSN: |
1098-4402 |
| DOI: |
10.1103/PhysRevSTAB.13.080706 |
| Popis: |
Three-dimensional simulation of harmonic up-conversion in a free-electron laser amplifier operating simultaneously with two cold and relativistic electron beams with different energy is presented in the steady-state regime. The fundamental resonance of the higher energy beam is adjusted at the third harmonic of the lower energy beam. By using slowly varying envelope approximation, the hyperbolic wave equations can be transformed into parabolic diffusion equations. By applying the source-dependent expansion to these equations, electromagnetic fields are represented in terms of the Hermite Gaussian modes which are well suited for the planar wiggler configuration. The electron dynamics is described by the fully three-dimensional Lorentz force equation in the presence of the realistic planar magnetostatic wiggler and electromagnetic fields. A set of coupled nonlinear first-order differential equations is derived and solved numerically. This set of equations describes self-consistently the longitudinal spatial dependence of radiation waists, curvatures, and amplitudes together with the evaluation of the electron beam. The evolutions of the transverse modes, in this system, are investigated for the fundamental resonance and its harmonic up-conversion. In addition to uniform beam, prebunched electron beam has also been studied. The effect of sinusoidal distribution of entry times for low energy electron beam on the evolution of radiation is compared with water bag distribution. It is shown that prebunching reduces the saturation length substantially. The analysis is related to extreme ultraviolet and x-ray emission where by seeding the lower frequency of the fundamental resonance of the lower energy beam substantial power is obtained at its third harmonic. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
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