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Chinese Physics B 2014年第3期23卷 244-248页

作者： s.saviz M.Karimi Plasma Physics Research Center Science and Research Branch Islamic Azad University

The effects of self-fields on electron trajectories and gain in planar wiggler free-electron lasers with two-stream and ion-channel guiding are investigated. An analysis of the two-stream quasi-steady-state electron trajectories is given by solving the equation of motion in the presence of ion-channel guiding and the planar wiggler. The electron trajectories and the gain are derived. The stability of the trajectories, the characteristics of the linear gain, and the normalized maximum gain are studied numerically. The numerical calculations show that there are eight group trajectories rather than the two groups reported in the absence of the self-fields. It is also shown that the normalized gain group seven （G7） decreases while the rest increases with the increase in normalized ion-channel frequency. The two-stream instability and the self-field lead to a decrease in the maximum gain, except for G7.

关键词： two-stream free-electron laser

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

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Chinese Physics B 2010年第1期19卷 366-371页

作者： H.Mehdian s.saviz Department of Physics and Institute for Plasma Research Tarbiat Moallem University Plasma Physics Research Center Science and Research CampusIslamic Azad University

A theory of a two-stream flee-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 J20. Furthermore, it is found that the two-stream laser with seff-field enhances the maximum gain in comparison with the single stream case.

关键词： free electron laser two-stream

Effects of self-fields on dispersion relation and growth rate in two-stream electromagnetically pumped free electron laser with axial guide magnetic field

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Chinese Physics B 2013年第12期22卷 243-247页

作者： s.saviz H.Rajabalinia Plasma Physics Research Center Science and Research Branch Islamic Azad University

A theory for a two-stream free-electron laser （FEL） with an electromagnetic wiggler （EMW） and axial guide magnetic field is developed. In the analysis, the effects of self-fields are taken into account. The growth rate is derived. The characteristics of the growth rate are studied numerically. The dependence of the normalized wave number, which corresponds to the maximum growth rate, on the cyclotron frequency is presented. The comparisons between the normalized maximum growth rate and its corresponding wave number normalized by employing the axial magnetic field, for the cases with and without self-fields in the two-stream FEL are studied numerically.

关键词： two-stream free electron laser

The effects of self-fields on the electron trajectory in a two-stream free electron laser with a helical wiggler and an axial guiding magnetic field

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Chinese Physics B 2012年第10期21卷 251-254页

作者： s.saviz E.Lashani Farzin M.Aghamir Plasma Physics Research Center Science and Research BranchIslamic Azad UniversityTehranP.O.Box 14665-678Iran Department of Physics University of TehranN.Kargar AveTehran 14399Iran

A theory for the two-stream free-electron laser（TsFEL） with a helical wiggler and an axial guide magnetic field is *** the analysis,the effects of self-fields are taken into *** analysis of the two-stream steady-state electron trajectories is given by solving the equation of *** calculations show that there are seven groups of orbits in the presence of self-fields instead of two groups reported in the absence of *** stability of the trajectories is studied numerically.

关键词： two-stream free electron laser electron trajectory

Gain enhancement in two-stream free electron laser with a planar wiggler and an axial guide magnetic field

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Chinese Physics B 2012年第9期21卷 247-250页

作者： s.saviz Z.Rezaei Farzin M.Aghamir Plasma Physics Research Center Science and Research BranchIslamic Azad University Department of Physics University of Tehran

The theory for a two-stream free electron laser （FEL） consisting of a relativistic electron beam transported alongthe axis of a planar wiggler in the presence of an axial guiding magnetic field is proposed and investigated. The electron trajectories and the small signal gain are derived. The characteristic of the linear gain and the normalized maximum gain are studied numerically. The result shows that the normalized maximum gain is considerably enhanced in comparison with that of the single stream. The effect of the difference between the energies of the two beams in this configuration of FEL is also considered, and we find that the gain is affected by the energy differences between groups 1 and 2.

关键词： wo-stream free-electron laser

Effects of self-fields on electron trajectory and gain in two-stream electromagnetically pumped free-electron laser with ion channel guiding

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Chinese Physics B 2011年第7期20卷 158-164页

作者： s.saviz Farzin M.Aghamir H.Mehdian M.Ghorannevis Plasma Physics Research Center Science and Research BranchIslamic Azad UniversityTehranP.O.Box.14665-678Iran Department of Physics University of TehranN.Kargar AveTehran 14399Iran Department of Physics and Institute for Plasma Research Tarbiat Moallem University49Dr.Mofatteh avenueTehran 15614Iran

A theory for the two-stream free-electron laser with an electromagnetic wiggler （EMW） and an ion channel guiding is developed. In the analysis, the effects of self-fields have been taken into account. The electron trajectories and the small signal gain are derived. The stability of the trajectories, the characteristics of the linear gain and the normalized maximum gain are studied numerically. The dependence of the normalized frequency ω corresponding to the maximum gain on the ion-channel frequency is presented. The results show that there are seven groups of orbits in the presence of the self-fields, which are similar to those reported in the absence of the self-fields. It is also shown that the normalized gains of 2 groups decrease while the rest increase with the increasing normalized ion-channel frequency. Furthermore, it is found that the two-stream instability and the self-field lead to a decrease in the maximum gain except for group 4.

关键词： free electron laser two-stream

Effects of self-fields on gain in two-stream free electron laser with helical wiggler and an axial guiding magnetic field

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Chinese Physics B 2014年第2期23卷 238-241页

作者： saviz s Lashani E Ashkarran A Plasma Physics Research Center Science and Research BranchIslamic Azad University Department of Physics Faculty of Basic SciencesUniversity of Mazandaran

The theory for the two-stream free electron laser （FEL） consisting of a relativistic electron beam transporting along the axis of a helical wiggler in the presence of an axial guiding magnetic field is proposed and investigated. In the analysis, the effects of self-fields are taken into account. The electron trajectories and the small signal gain are derived. The characteristics of the linear-gain and the normalized maximum gain are studied numerically. The results show that there are seven stable groups of orbits in the presence of self-fields instead of two groups reported in the absence of the self-fields. It is also shown that the normalized gains of three groups decrease while the rest increase with the increasing of normalized cyclotron frequency g20. Furthermore, it is found that the two-stream instability and the self-field lead to a decrease in the maximum gain except for group 3. The results show that the normalized maximum gain is enhanced in comparison with that of the single stream.

关键词： two-stream free electron laser