Laser-plasma lens for laser-wakefield accelerators

Abstract

International audienceThanks to their compactness and unique properties, laser-wakefield accelerators are currently considered for several innovative applications. However, many of these applications—and especially those that require beam transport—are hindered by the large divergence of laser-accelerated beams. Here we propose a collimating concept that relies on the strong radial electric field of the laser-wakefield to reduce this divergence. This concept utilizes an additional gas jet, placed after the laser-wakefield accelerator. When the laser pulse propagates through this additional gas jet, it drives a wakefield which can refocus the trailing electron bunch. Particle-in-cell simulations demonstrate that this approach can reduce the divergence by at least a factor of 3 for realistic electron bunches

Laser–plasma acceleration of electrons for radiobiology and radiation sources

“…3. This mismatch limits the maximum electron energy [22] and the short acceleration length affects the downstream angular divergence [23,24] of the electron beam due to the negligible action of transverse focusing fields.…”

Effects of the dopant concentration in laser wakefield and direct laser acceleration of electrons

“…The time step corresponds to 52 as, and three Fourier modes are used for the fields in the azimuthal direction. Furthermore it has been shown that the interpolation of the magnetic field in the PIC lattice can induce a spurious force that increases the transverse momentum of the accelerated particles that propagate inside the plasma wave [28]. To avoid these non-physical forces, the second-order time-interpolation method used by Lehe et al [28] is applied here.…”

Laser-plasma interactions with a Fourier-Bessel particle-in-cell method

“…These result from the artificial high-frequency electromagnetic waves, which in FDTD are significantly slowed by numerical diffraction, and are generated by the relativistic particles, in a way similar to the physical Cherenkov radiation in the dispersive media. The numerical Cherenkov effect, along with the errors of Lorentz force projection, are known to also increase beams emittance in the wakefield acceleration simulations 4,7 . The particles transverse velocities FDTD is significantly affected by the numerical effects (see upper left of fig.…”

“…In this case, the terms E p and β p × B p of the Lorentz force, with which wave acts on the particle, may compensate each other with a reminder F p ∼ eE p /γ 2 p , where γ p = (1 − β 2 p ) −1/2 is the particle's Lorentz factor. For a relativistic particle, the force F p can be very small, and for the correct projection of the staggered fields a very fine temporal and spatial resolutions may be required 7 . The mentioned issues become especially important in modeling the wakefield acceleration of particles (WFA).…”