Acceleration and evolution of a hollow electron beam in wakefields driven by a Laguerre-Gaussian laser pulse

Abstract

We show that a ring-shaped hollow electron beam can be injected and accelerated by using a Laguerre-Gaussian laser pulse and ionization-induced injection in a laser wakefield accelerator. The acceleration and evolution of such a hollow, relativistic electron beam are investigated through three-dimensional particle-in-cell simulations. We find that both the ring size and the beam thickness oscillate during the acceleration. The beam azimuthal shape is angularly dependent and evolves during the acceleration. The beam ellipticity changes resulting from the electron angular momenta obtained from the drive laser pulse and the focusing forces from the wakefield. The dependence of beam ring radius on the laser-plasma parameters (e.g., laser intensity, focal size, and plasma density) is studied. Such a hollow electron beam may have potential applications for accelerating and collimating positively charged particles

Polarized electron-beam acceleration driven by vortex laser pulses

“…The vortex beam produces a donut-shaped electron bunch in the vicinity of r 0 ±!r/2, as compared to a cylinder-like beam of radius !r for the Gaussian driver, corresponding to a cross-section area of 2πr 0 !r and π!r 2 , respectively. For a simple estimation, we use !r∼a 1/2 λ p (x p )/π∼4 μm [30,[48][49][50] as the bunch radius of the trapped electrons and r 0 =w 0 / 2 ≈7 μm as the center of the trapped region for the LG case [48,49]. Accordingly, the peak-current ratio between the LG and the Gaussian case is about 2r 0 /!r∼3.5, a factor that is well reproduced in simulations.…”

“…In LWFA, one usually has B∼B f , E r ∼−B f and v∼v x [47,49], where B f is the azimuthal magnetic field within the bubble. Considering γ∼1 ?a e during the injection (see figure 3(a)), the spin precession frequency from equation (2) takes the simplified form Ω≈eB f (2+β x )/2me f .…”

“…Therefore, the field strength depends on two quantities: the longitudinal current density (J x ) and the electric field (E x ) along the x axis. Since it is known for the blow-out regime that |j x /ε 0 c 2 |/|∂E x /c∂x|∼n p /n 0 ∼4 [49][50][51], the difference is mainly due to the self-generated magnetic field of the beam current. For a Gaussian laser, the light intensity peaks on-axis such that trapped electrons are concentrated at the center of the bubble, leading to a well-directed current in the counter-propagation direction, as shown in figure 4(d).…”

Optimal Laguerre–Gaussian modes for high-intensity optical vortices

“…As the OAM of a photon is theoretically unbounded, the ability for a single photon to carry multiple units of angular momentum has drawn large interest, particularly in the fields of communication multiplexing [8], particle trapping [9], and laser-plasma interactions [10][11][12][13][14]. Interest in high-power and high-intensity OAM beams has been largely explored theoretically and in particular, its interaction with plasma for enhancement of particle guiding [15,16], highharmonic generation [17,18], and magnetic field generation [19,20]. Experimental demonstration of high-intensity OAM beams has been hindered due to difficulties associated with generating OAM beams in HPL systems.…”

Numerical study of the wave-break in the vacuum-plasma interface during the interaction of an intense laser pulse

“…In this context, a vast number of wave-particle phenomena become particularly interesting when the high power laser causes the electron quiver velocity to become highly relativistic. Among these phenomena, the wake field's generation, [1][2][3][4][5][6] scattering and modulation of the laser pulse, [7][8][9][10] stochastic motion of the electrons [11][12][13][14][15] and wave breaking processes [16][17][18][19] have attracted growing interest due to their vital role in the concept of laser-plasma accelerator. The last case, the wave breaking effect, is one of the most fundamental phenomena in the laser-plasma concept and it is the basis of some chaotic motion of electrons and also acceleration mechanisms such as acceleration initiated by the fluid wave breaking, direct laser acceleration, and acceleration originated from the nonlinear wave breaking via the plasma-vacuum boundary effect.…”