中国物理B ›› 2010, Vol. 19 ›› Issue (1): 14214-014214.doi: 10.1088/1674-1056/19/1/014214

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The effects of self-fields on the electron trajectory and gain in a two-stream electromagnetically pumped free-electronlaser with axial guiding field

H.Mehdian1, S.Saviz2   

  1. (1)Department of Physics and Institute for Plasma Research, Tarbiat Moallem University, 49, Dr. Mofatteh avenue, Tehran 15614, Iran; (2)Plasma Physics Research Center, Science and Research Campus, Islamic Azad University, Tehran, P.O. Box: 14665-678, Iran
  • 收稿日期:2009-01-12 修回日期:2009-07-14 出版日期:2010-01-15 发布日期:2010-01-15

The effects of self-fields on the electron trajectory and gain in a two-stream electromagnetically pumped free-electronlaser with axial guiding field

H. Mehdiana)† and S. Savizb)   

  1. a Department of Physics and Institute for Plasma Research, Tarbiat Moallem University, 49, Dr. Mofatteh avenue, Tehran 15614, Iran; b Plasma Physics Research Center, Science and Research Campus, Islamic Azad University, Tehran, P.O. Box: 14665-678, Iran
  • Received:2009-01-12 Revised:2009-07-14 Online:2010-01-15 Published:2010-01-15

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摘要： A theory of a two-stream free-electron laser in a combined electromagnetic wiggler (EMW) is developed, in which we use an axial-guide magnetic field and take into account the effects of the self-fields. The electron trajectories and the small signal gain are derived. The stability of the trajectories, the characteristics of the linear-gain, and the normalised maximum gain are studied numerically. The results show that there are nine stable groups of orbits in the presence of self-fields instead of seven groups reported in the absence of the self-field. It is also shown that the normalised gains of four groups of the orbits are decreasing and those for the rest of them are increasing with growing \barΩ0. Furthermore, it is found that the two-stream laser with self-field enhances the maximum gain in comparison with the single stream case.

Abstract: A theory of a two-stream free-electron laser in a combined electromagnetic wiggler (EMW) is developed, in which we use an axial-guide magnetic field and take into account the effects of the self-fields. The electron trajectories and the small signal gain are derived. The stability of the trajectories, the characteristics of the linear-gain, and the normalised maximum gain are studied numerically. The results show that there are nine stable groups of orbits in the presence of self-fields instead of seven groups reported in the absence of the self-field. It is also shown that the normalised gains of four groups of the orbits are decreasing and those for the rest of them are increasing with growing $\bar{\varOmega}_0$. Furthermore, it is found that the two-stream laser with self-field enhances the maximum gain in comparison with the single stream case.

Key words: free electron laser, two-stream

中图分类号:  (Free-electron lasers)

  • 41.60.Cr
42.55.Ah (General laser theory)