Articles written in Pramana – Journal of Physics
Volume 76 Issue 3 March 2011 pp 489-500
Self-ﬁeld effects, induced by charge and current densities of the electron beam, on gain in two-stage free-electron laser with nonuniform guide magnetic ﬁeld is presented. The gain equation for small-signal has been derived analytically. The results of numerical calculations show a gain decrement for group I orbits and a gain enhancement for group II orbits, due to the self-ﬁeld effects. The wiggler-induced self-magnetic ﬁeld has a diamagnetic effect for group I orbits, whereas for group II, it has a paramagnetic effect. It is also found that using a nonuniform guide ﬁeld, rather than a uniform one, causes the gain to increase.
Volume 82 Issue 6 June 2014 pp 1049-1060 Research Articles
The operative mechanism for a free-electron laser (FEL) with two consecutive helical wigglers having opposite circular polarization in the presence of an axial magnetic field is proposed and analysed. With the help of fluid theory, a tenth-degree polynomial dispersion equation for electromagnetic and space-charge waves is derived. The results are used to illustrate and discuss the dependence of growth rate on different system parameters. Finally, it is shown that for the same system parameters the growth rate of the proposed structure is more than the growth rate of instability in a conventional FEL.
Volume 93 | Issue 5
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