Beam manipulation for compact laser wakefield accelerator based free-electron lasers

Abstract

Free-electron lasers (FELs) are a unique source of light, particularly in the x-ray domain. After the success of FELs based on conventional acceleration using radio-frequency cavities, an important challenge is the development of FELs based on electron bunching accelerated by a laser wakefield accelerator (LWFA). However, the present LWFA electron bunch properties do not permit use directly for a significant FEL amplification. It is known that longitudinal decompression of electron beams delivered by state-of-the-art LWFA eases the FEL process. We propose here a second order transverse beam manipulation turning the large inherent transverse chromatic emittances of LWFA beams into direct FEL gain advantage. Numerical simulations are presented showing that this beam manipulation can further enhance by orders of magnitude the peak power of the radiation.g 0 with P 0 the input noise power coupled into the dominant amplified mode and L g the gain length given by:

Electron and photon diagnostics for plasma acceleration-based FELs

“…To deal with those realistic high energy spread and high divergence, three techniques have been proposed: horizontally disperse and couple the beam in a Transverse Gradient Undulator (Huang et al, 2012), decompress and couple the beam in a suitably tapered undulator (Maier et al, 2012;Seggebrock et al, 2013;Couprie et al, 2014) and finally decompress and synchronize the beam waist advance with the FEL slippage (Loulergue et al, 2015). While previous methods have never been implemented, the chromatic matching is presently being tested on COXINEL (Couprie et al, 2016).…”

Free-electron lasers driven by laser plasma accelerators

“…The COXINEL collaboration [21] at SOLEIL/LOA near Paris, France, is relying on transport through a chicane and into a 5-m planar undulator (without strong-focusing). To improve FEL gain and make efficient use of the energy spread, a chromatic transport scheme [22,23] is proposed where the various electron energies are focused at various locations within the undulator. This chromatic separation is optimized such that the FEL radiation pulse keeps slipping into a focused electron population (labeled "chromatic matching").…”

Wide-angle electron beams from laser-wakefield accelerators

“…6 Only a small fraction of plasma electrons can be injected into the bubble and laser-wakefield accelerators typically produce beams with a small charge at pC level, which is desirable when high-quality beams with short bunch length, narrow energy spread and low emittance are required, for novel radiation sources. [7][8][9][10][11][12][13][14] There are, however, applications such as non-destructive-testing, ultra-fast studies in condensed matter, radiolysis, isotope production and radiotherapy that require high-charge, low-energy electron beams. [15][16][17][18][19] Ionization-assisted injection in high-Z or clustering gas targets has been explored to boost the charge to 100s pC at 10s-100s MeV energies.…”