Quasi-monoenergetic femtosecond photon sources from Thomson Scattering using laser plasma accelerators and plasma channels

Abstract

Narrow bandwidth, high energy photon sources can be generated by Thomson scattering of laser light from energetic electrons, and detailed control of the interaction is needed to produce high quality sources. We present analytic calculations of the energy-angular spectra and photon yield that parametrize the influences of the electron and laser beam parameters to allow source design.These calculations, combined with numerical simulations, are applied to evaluate sources using conventional scattering in vacuum and methods for improving the source via laser waveguides or plasma channels. We show that the photon flux can be greatly increased by using a plasma channel to guide the laser during the interaction. Conversely, we show that to produce a given number of photons, the required laser energy can be reduced by an order of magnitude through the use of a plasma channel. In addition, we show that a plasma can be used as a compact beam dump, in which the electron beam is decelerated in a short distance, thereby greatly reducing radiation shielding. Realistic experimental errors such as transverse jitter are quantitatively shown to be tolerable. Examples of designs for sources capable of performing nuclear resonance fluorescence and photofission are provided. * SRykovanov@lbl.gov † CGRGeddes@lbl.gov

Narrowband inverse Compton scattering x-ray sources at high laser intensities

“…It is remarkable that the optimal frequency modulation is not influenced by the electron recoil, as Eq. (31) does not depend on the electron recoil parameter χ, while the equation for the local x-ray frequency (26) that is used to define the compensation condition does depend on the recoil.…”

“…This we conclude from the fact that the chirping prescription (34), does not depend on the harmonic number , although we derived it from the general expression for the frequency of the -th harmonic, Eq. (26).…”

“…[26,30,48], the x-ray frequency ω is conveniently normalized to the on-axis x-ray frequency in recoil-free linear Thomson scattering as y = ω /4γ 2 ω 0 . A numerical example for the compensation of the ponderomotive broadening and the narrowing of the spectral lines is exhibited in Fig.…”

“…a large number of photons in a narrow spectral bandwidth [19][20][21][22][23]. It is therefore essential to achieve a good control over all parameters that contribute to the bandwidth to minimize their influence [24][25][26]. In the linear regime (i.e.…”

“…This ponderomotive broadening is a nonlinear finite-pulse-length effect that is relevant whenever the laser bandwidth is small enough to resolve the ponderomotive red-shift of the scattered radiation [24,31]. Thus, one needs to keep the laser intensity low enough for the bandwidth requirements, which limits the x-ray's spectral brightness [24,26]. Recently, it was proposed to compensate the ponderomotive broadening by using suitably chirped initial laser pulses [30,32], which would allow to operate the Compton sources in the high-intensity regime.…”