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Sources of Radiation
Published in Douglas S. McGregor, J. Kenneth Shultis, Radiation Detection, 2020
Douglas S. McGregor, J. Kenneth Shultis
Because the electrons are highly relativistic, the synchrotron radiation is emitted in a very narrow cone in the direction of electron travel as they are deflected. Undulators cause the beam to be deflected sinusoidally by a weak oscillatory magnetic field, thereby producing nearly monochromatic photons. By contrast, a wiggler uses a strong oscillatory magnetic field which, because of relativistic effects, produces distorted sinusoidal deflections of the electron beam and synchrotron radiation with multiple harmonics, i.e., a line spectrum. If very strong magnetic fields are used, many harmonics are produced that merge to yield a continuous spectrum ranging from the infrared to hard x rays. By placing undulators or wigglers at a specific location in the storage ring, very intense and narrowly collimated beams of photons with energies up to a few keV can be produced, useful in x-ray diffraction analyses.
Light Sources
Published in Andrei Seryi, Unifying Physics of Accelerators, Lasers and Plasma, 2015
The third-generation employs insertion devices (undulators and wigglers). Either of these devices is a periodic array of magnetic poles that provide a sinusoidal magnetic field B on axis: B = (0, B0 sin(kuz), 0) where ku = 2π/λu. The maximal radius of the curvature of the orbit in the sinusoidal field R defines two distinct regimes (see Section 3.3.5). If 2R/γ ≪ λu/2 (parameter K ~ γ λu/R >> 1), then the radiation emitted at each period of sin-like field is independent; this corresponds to a wiggler regime (similar to radiation from a sequence of bends). The insertion devices working in a wiggler regime are usually used to achieve high photon energies and flux.
High gain free electron laser with waveguide
Published in R A Cairns, A D R Phelps, P Osborne, Generation and Application of High Power Microwaves, 2020
The fundamental role of the wiggler is to provide a transverse velocity component to the electrons, thus allowing their coupling with the electric field. From the relativistic equation describing the energy variation of an electron interacting with an e.m. wave we have dγdt=−emcE.β=−emcE⊥.β⊥
Trajectories in relativistic electron beam with elliptical cross section under the effects of self-fields, axial, planar and helical wiggler magnetic fields
Published in Waves in Random and Complex Media, 2022
F. S. Abdollahi, A. Abdoli-Arani, T. Mohsenpour
The physical mechanism of the free electron laser (FEL) depends on the propagation of an electron beam through a periodic magnetic field [11]. On the other hand, the field of an FEL with HWMF was investigated by many researchers [12–35]. On the other hand, this interaction occurs when a cold intense relativistic electron beam and waves pass through a wiggler magnetic field [12–25,36–38]. In this regime, so called the Raman regime, that is related to the high-density and low-energy of the electron beam, an axial magnetic field is usually applied to guide the electron beam. In this field, the electrostatic stability of electron beam modes has been studied with considering a relativistic plasma with HWMF [26–28]. Furthermore, the propagation of space-charge and electromagnetic waves through combined helical wiggler and axial guide magnetic fields has been studied [29–31]. Instability of wave modes in a two-stream FEL with an axial magnetic field [32], instability of wave modes in a free-electron laser with background plasma under influence of self-field effects [33] and mode couplings in a two-stream FEL with HWMF and an ion channel guiding have also been investigated [34]. Although there is considerable literature on the theory of planar wiggler FEL, most treatments heretofore have neglected the influence of the self-fields [35,39–44]. A wiggler with helically symmetric magnetic field generated by bifilar current windings currently is employed by many FELs. A planar wiggler with a linearly symmetric magnetic field generated by alternating stacks of permanent magnets is sometimes used as an alternative to the helical wiggler. A uniform static axial magnetic field is often employed to guide the propagation of electron beam through the wiggler and to enhance the gain. Both of self-electric and self-magnetic fields are induced by the steady-state charge and current densities of the non-neutral electron beam. However, self-fields are known to have significant effects on the FEL operation [11]. The effect of self-fields in an FEL with planar wiggler and axial magnetic field that play a significant role in altering the electron dynamics [45] has been studied. Furthermore, electron orbits in an FEL with planar wiggler, axial magnetic field have been investigated [46].