Plasma wakefield accelerator driven coherent spontaneous emission from an energy chirped electron pulse

Abstract

Plasma accelerators (Esary et al 2009 Rev. Mod. Phys. 81 1229) are a potentially important source of high energy, low emittance electron beams with high peak currents generated within a relatively short distance. As such, they may have an important application in the driving of coherent light sources such as the Free Electron Laser (FEL) which operate into the x-ray region (McNeil and Thompson 2010 Nat. Photon. 4 814-21). While novel plasma photocathodes (Hidding et al 2012 Phys. Rev.Lett. 108 035001) may offer orders of magnitude improvement to the normalized emittance and brightness of electron beams compared to Radio Frequency-driven accelerators, a substantial challenge is the energy spread and chirp of beams, which can make FEL operation impossible. In this paper it is shown that such an energychirped, ultrahigh brightness electron beam, with dynamically evolving current profile due to ballistic bunching at moderate energies, can generate significant coherent radiation output via the process of Coherent Spontaneous Emission (CSE) (Campbell and McNeil 2012 Proc. FEL2012 (Nara, Japan)). While this CSE is seen to cause some FEL-induced electron bunching at the radiation wavelength, the dynamic evolution of the energy chirped pulse dampens out any high-gain FEL interaction. This work may offer the prospect of a future plasma driven FEL operating in the high-gain Self Amplified CSE mode.

Ultrahigh brightness beams from plasma photoguns

“…While the applications of ultralow emittance and ultrabright electron beams are too numerous and wide-reaching to discuss them adequately here, we highlight two major thrusts: First, both the ultralow emittance, and ultrahigh brightness potential of plasma photocathodes makes them ideal candidates at the heart of advanced photon sources such as soft X-ray coherent synchrotron radiation sources [51,52], hard X-ray FEL, betatron radiation and ion channel lasers [31,32], and γ-ray sources [32]. Second, such beams could be spearheading R&D towards high energy physics colliders.…”

Free electron lasers driven by plasma accelerators: status and near-term prospects

“…From the conception of plasma photocathodes 10 years ago and the first vision towards a hard plasma-based X-FEL [ 23 ] , systematic R&D towards plasma-based X-FEL [ 82 ] has included innovations such as multi-color X-FELs and ballistic compression/stretching [ 83 ] , energy spread control [ 78 ] , coherent spontaneous emission-based light sources [ 84 ] , and various other concepts [ 79 , 81 ] . Although a proposal for ‘plasma-based hard X-ray FEL with ultrahigh gain and sub-fs capability’ at SLAC FACET-II was deemed ahead of its time in 2018, experimental progress on high-brightness beam production from PWFA via the plasma photocathode and plasma torch method at SLAC [ 30 , 76 ] and at DESY via the plasma torch method [ 85 ] , and from hybrid LWFA PWFA [ 86 – 89 ] , increased confidence in the overall approach [ 82 ] , and various start-to-end design breakthroughs (A. F. Habib et al , forthcoming) now put dedicated experimental efforts for next-generation electron beam sources for photon science [ 90 ] and hard plasma X-FEL on the agenda.…”

A coherent harmonic generation method for producing femtosecond coherent radiation in a laser plasma accelerator based light source

“…Furthermore, spontaneous undulator radiation from LPA beams has been observed experimentally (Schlenvoigt et al, 2008;Fuchs et al, 2009;Anania et al, 2014;André et al, 2018). Stepping further, the forthcoming experiments may focus on coherent undulator radiation (Labat et al, 2020;Alotaibi et al, 2020). Some coherent harmonic generation (CHG) methods (Feng et al, 2015;Feng et al, 2018;Liu et al, 2019) have been proposed to achieve this goal.…”