An application of laser–plasma acceleration: towards a free-electron laser amplification

Abstract

The laser-plasma accelerator (LPA) presently provides electron beams with a typical current of a few kA, a bunch length of a few fs, energy in the few hundred MeV to several GeV range, a divergence of typically 1 mrad, an energy spread of the order of 1%, and a normalized emittance of the order of π.mm.mrad. One of the first applications could be to use these beams for the production of radiation: undulator emission has been observed but the rather large energy spread (1%) and divergence (1 mrad) prevent straightforward free-electron laser (FEL) amplification. An adequate beam manipulation through the transport to the undulator is then required. The key concept proposed here relies on an innovative electron beam longitudinal and transverse manipulation in the transport towards an undulator: a 'demixing' chicane sorts the electrons according to their energy and reduces the spread from 1% to one slice of a few ‰ and the effective transverse size is maintained constant along the undulator (supermatching) by a proper synchronization of the electron beam focusing with the progress of the optical wave. A test experiment for the demonstration of FEL amplification with an LPA is under preparation. Electron beam transport follows different steps with strong focusing with permanent magnet quadrupoles of variable strength, a demixing chicane with conventional dipoles, and a second set of quadrupoles for further focusing in the undulator. The FEL simulations and the progress of the preparation of the experiment are presented.

Measured Emittance Dependence on the Injection Method in Laser Plasma Accelerators

“…Owing to their ability to accelerate electron beams to GeV-class energies over cm-scale distances with fsscale bunch durations and ultra low emittances [1], laser plasma accelerators (LPAs) are poised to usher in a new era of compact accelerator driven applications. Compact LPA-based x-ray FELs [2][3][4][5], compact monoenergetic MeV-class Thomson-scattered photons [6,7], and progress towards an LPA-based electron-positron collider [8], are actively pursued. Most LPA-based applications require excellent 6D electron beam brightness, defined as B 6D = I b / (σ E x y ) where I b is the peak beam current, σ E is the energy spread, and x,y are the normalized transverse emittances (herein referred to simply as emittance).…”

Towards compact Free Electron–Laser based on laser plasma accelerators

“…7) are under way. The COXINEL (SOLEIL, LOA, PhLAM, France) [197,198,199] project, part of the LUNEX5 one [200,201] aims at FEL amplification at 200 nm at typically 180 MeV, before increasing the energy up to 400 MeV for radiation down to 40 nm. Electrons are generated by the "salle Jaune" 2x60 TW laser in ionization configuration (see Fig.…”

Plasma boosted electron beams for driving Free Electron Lasers

“…Moreover, they may also suffer from unacceptable jitters in final energy, charge and pointing. Nevertheless, in the FEL framework, there exist the possibility to perform a chromatic matching [8] to take advantage of the typical structure of internally injected longitudinal phase space beams and a recent project, named COXINELL [9], aims at demonstrating experimental feasibility.…”