Dense Helical Electron Bunch Generation in Near-Critical Density Plasmas with Ultrarelativistic Laser Intensities

Abstract

The mechanism for emergence of helical electron bunch(HEB) from an ultrarelativistic circularly polarized laser pulse propagating in near-critical density(NCD) plasma is investigated. Self-consistent three-dimensional(3D) Particle-in-Cell(PIC) simulations are performed to model all aspects of the laser plasma interaction including laser pulse evolution, electron and ion motions. At a laser intensity of 1022 W/cm2, the accelerated electrons have a broadband spectrum ranging from 300 MeV to 1.3 GeV, with the charge of 22 nano-Coulombs(nC) within a solid-angle of 0.14 Sr. Based on the simulation results, a phase-space dynamics model is developed to explain the helical density structure and the broadband energy spectrum.

Manipulating the topological structure of ultrarelativistic electron beams using Laguerre–Gaussian laser pulse

“…In this case, the resonant electrons in the plasma bubble are locked in the acceleration phase of CP laser field and they experience circular motions collectively together with the rotating CP laser field. As a result, the energy density of the accelerated electron beam exhibits an annular distribution, as shown in figure 2(a), which also agrees well with previous simulation results using CP Gaussian laser pulse [17,45]. However, for l 0 ¹ , the results are quite different from the case with l=0.…”

“…Figure 4 shows the Hamiltonian and trajectories of electrons in phase-space (θ, γ) for a fixed laser propagation phase of f L =π. It is shown from figure 4(a) that there is only one fixed point and one separatrix for the case of l=0, which is consistent with the previous work [45]. While for the LG laser pulse with l 0 ¹ , the number of fixed points is related to the topological charge of the laser pulse and is equal to l+1, as shown figures 4(b) and (c), which agrees well with the above theoretical estimates.…”

“…)is the amplitude of the LG laser pulse. In this case, the self-injected electrons can interact with the laser field directly when they are accelerated by the longitudinal charge-separation electric field [44,45].…”

“…For relativistic betatron electrons with γ?1, κ, k B and k E can be treated as constants as they are slow variables compared to the fast oscillating variables[17,[45][46][47]. In this case, a Hamiltonian that describes the electron dynamics in phase-space (ψ, γ) can be derived as…”

Brilliant petawatt gamma-ray pulse generation in quantum electrodynamic laser-plasma interaction

“…However, for laser interaction with steep solid density targets, where no preplasmas exist, the γ -ray emission occurs only in the small skin-depth region2262728, therefore, the conversion efficiency from laser to γ -rays is still low, and the peak brightness of γ -rays is also limited. Recently, a self-matching resonance acceleration scheme3233 in near-critical plasmas by circularly polarized laser pulses has been explored, which can generate much denser relativistic electron beams than the case of direct laser acceleration with linearly polarized lasers3435. However, the laser intensity used there is comparatively low in the non-QED regime, electron resonance acceleration is dominantly governed by only the self-generated electromagnetic fields in the plasma, which limits both the energy and the density of the electron bunch for synchrotron radiation.…”