Self-ﬁeld effects on small-signal gain in two-stage free-electron lasers
S Jafari H Mehdian A Hasanbeigi
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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.
S Jafari1 H Mehdian1 A Hasanbeigi1
Volume 97, 2023
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