The effects of self-fields on the electron trajectory and gain in a two-stream electromagnetically pumped free-electronlaser with axial guiding field |
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Authors: | H Mehdian and S Saviz |
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Institution: | Department of Physics and Institute for Plasma Research, Tarbiat Moallem University, 49, Dr. Mofatteh avenue, Tehran 15614, Iran; Plasma Physics Research Center, Science and Research Campus, Islamic Azad University, Tehran, P.O. Box: 14665-678, Iran |
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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. |
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Keywords: | free electron laser two-stream |
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