Plasma Undulator Based on Laser Excitation of Wakefields in a Plasma Channel

Flexible x-ray source with tunable polarization and orbital angular momentum from Hermite-Gaussian laser modes driven plasma channel wakefield

“…In case (3), the oscillation is helical. One can see a behavior that is very similar to the case of a Gaussian laser pulse injected into the parabolic channel with some initial centroid displacement or with some angle with respect to the channel axis, which is discussed in detail in previous works [37,40,41,47]. From Eq.…”

“…2(a), the projection of the transverse wakefield on thexẑ plane, E x , is generated by two different modes without the condition (12). The electron in such a wakefield undergoes both betatron and undulator oscillations and can be treated in the same way as in our previous work [37,40,41], where the electron beam principally undergoes an envelope oscillation due to the betatron focusing force. Such oscillation will give rise to the spread of momentum and energy of the electron beam, and subsequently broaden the radiation spectrum as discussed later.…”

“…It was also mentioned that using the superposition of two (odd and even) higher-order Hermite-Gaussian modes may (1) lead to a better control over the strength of the focusing forces, relaxing the conditions for the electron beam emittance for generation of a narrow-bandwidth photon spectrum; and (2) provide more control for the parameters of the plasma undulator (its strength and wavelength). It is the purpose of this paper to extend previous work [37,39,41] and provide detailed analytical derivations for the case where the plasma undulator is created by the superposition of higher-order laser modes propagating inside the parabolic plasma channel. It will also show that our scheme is capable of generating harmonics carrying OAM in the circularly polarized undulator.…”

“…The plasma undulator or wiggler (PIGGLER) is based on wakefields created by the laser pulse undergoing centroid oscillations in a plasma channel [37][38][39][40]. Detailed linear theory for the case of a Gaussian laser pulse injected with some initial offset and/or with some initial angle relative to the plasma channel symmetry axis has been developed [37,41]. It has been shown, that an electron beam correctly injected in the wakefield structure oscillates with the characteristic undulator wavelength equal to λ u ¼ 2πZ R , where Z R is the Rayleigh length of the laser pulse.…”

Enhanced betatron radiation by steering a laser-driven plasma wakefield with a tilted shock front

“…Some ideas of manipulating r b to enhance betatron radiation have been demonstrated; [18][19][20][21][22] however, the produced x-rays had continuum spectra because the controllability was at the cost of sacrificing the e-beam quality. Recently, an idea of a helical plasma undulator has been proposed to produce controllable synchrotron-like radiation by inducing centroid oscillations of the laser pulse 23,24 in a plasma channel. Furthermore, some methods have also been proposed to obtain bright betatron x-rays by applying an external ultra-intense magnetic field 25,26 in the wakefield but have not been demonstrated experimentally so far.…”