On some theoretical problems of laser wake-field accelerators

Abstract

Enhancement of the quality of laser wake-field accelerated (LWFA) electron beams implies the improvement and controllability of the properties of the wake waves generated by ultra-short pulse lasers in underdense plasmas. In this work we present a compendium of useful formulas giving relations between the laser and plasma target parameters allowing one to obtain basic dependences, e.g. the energy scaling of the electrons accelerated by the wake field excited in inhomogeneous media including multi-stage LWFA accelerators. Consideration of the effects of using the chirped laser pulse driver allows us to find the regimes where the chirp enhances the wake field amplitude. We present an analysis of the three-dimensional effects on the electron beam loading and on the unlimited LWFA acceleration in inhomogeneous plasmas. Using the conditions of electron trapping to the wake-field acceleration phase we analyse the multi-equal stage and multiuneven stage LWFA configurations. In the first configuration the energy of fast electrons is a linear function of the number of stages, and in the second case, the accelerated electron energy grows exponentially with the number of stages. The results of the two-dimensional particle-in-cell simulations presented here show the high quality electron acceleration in the triple stage injection-acceleration configuration.

Similarity of magnetized plasma wake channels behind relativistic laser pulses with different wavelengths

“…Immediately after the laser has passed, the weakly perturbed electrons near the cavity boundary perform approximately radial plasma oscillations with angular frequency ω pe . In agreement with theoretical predictions for a 0 ∼ 1 [1,2,6], this produces a wake with characteristic wavelength λ wake (B ext = 0) ≈ 2πc/ω pe = λ pe ≈ 6 mm (25) behind the laser pulse moving away with velocity c. However, for the present combination of parameters, only the first half cycle is clearly visible in the form of a cavity because transverse wave breaking [33] dominates and overshadows the subsequent wakes, which have a D-shaped form but are not clearly visible in Fig. 2(a).…”

“…11(a), the differences are reduced when the box height is increased from L y = 2.4 mm to 3.2 mm. 6 Since we know from Fig. 10 that there are underresolved singular structures in the present simulations, we have also checked whether the spatial resolution affects the energy distribution in Fig.…”

“…The initial electron density is uniform, except for a narrow boundary layer, where it is ramped up or down. In mathematical form, it may be written as n e (x, y, z|t = 0) = n e0 × H(x|s x )H(y|s y )H(z|s z ), (6) with n e0 = 3 × 10 13 cm −3 and…”

“…Laser-induced wake waves [1] have been studied extensively during the last decades, in particular in the context of particle acceleration [2] and for the generation of compact sources of energetic photons [3,4,5]. Many interesting and useful applications have emerged, and there still exists much potential for expansion [6].…”

Wakefield excited by ultrashort laser pulses in near-critical density plasmas

“…[25][26][27][28][29][30][31][32] On the other hand, high repetition rate lasers are currently capable to deliver pulses only at multi-mJ energy level. According to the scaling laws of the blowout regime, 5,12,33 downscaling the LWFA to the mJ level calls for the use of extremely short laser pulses and high density plasmas. Typically, for a 1 TW laser system delivering pulses at wavelength λ 0 = 0.8 µm, one requires pulse of duration τ < 5 fs focused down to a spot of size w 0 ≈ 2 µm in a plasma of electron density n e ≈ 10 20 cm −3 .…”