High Power Laser Science and Engineering, Volume. 12, Issue 6, 06000e86(2024)
Electron injection and acceleration in a twisted laser driven by the light fan
Figures & Tables(8)
Fig. 1. The target features a ‘light fan’ structure and a nanowire structure (blue part) at the center. The ‘light fan’ has eight parts, each with a uniform step height of 
. This setup emulates the effect of a spiral phase plate with 
. The colors in green represent different phase changes that occur when a plane wave is incident normally. To prevent transmission of the laser pulse, the maximum thickness of the target is set to 1.6 μm.
Fig. 2. The longitudinal slices of the electric and magnetic field components of the twisted laser beam are generated by the reflection of the plasma and the electron density from the PIC simulation. Panels (a) and (c) show the longitudinal electromagnetic field 
and 
in the 
-plane at 
. Panel (b) shows 
at the same location. The dashed lines in (b) and (c) are cuts that will be displayed as line-outs in (e) and (f). Panel (d) shows the electron density and the longitudinal electric field, where the blue and red contour lines represent 
and 
, respectively. All the snapshots are taken at 
fs from the simulation with the parameters listed in 
(the cut shown as a dashed line at 
in (b)) and 
(the cut shown as a dashed line at 
in (c)), respectively. (f) The frequency spectra of 
(red curve) and 
(blue curve) from panel (e) were generated using the FFT. The dashed line represents the predicted attenuation curve of the high harmonic of the ROM mechanism 
.
Fig. 3. The transverse magnetic field distribution of each mode obtained from the mode decomposition of the simulation results at the same time of 
in the simulation in the 
-plane at 
fs. It is also the real part of the complex magnetic field 
in the 
plane, which is the raw data of the Hilbert transform used to obtain (b) and (c). (b) The distribution of the main mode with 
and 
. (c) The distribution of another mode with 
and 
.
Fig. 4. (a) 3D rendering of the electron density at 
fs, where the blue and red isosurfaces represent 
and 
, respectively. The early trajectories of some electrons, which were randomly selected from the central region in the third bunch at 
fs. The line color shows electron energy. (b) Representative electron trajectories in the 
transverse plane from time 
fs to time 
fs. Images (c) and (d) are the trajectories of the same electrons in the longitudinal plane of 
and 
, respectively.
Fig. 5. Acceleration results for the electron bunches in the reflected twisted beam. (a) The line density of electron bunches in the region of 
. The black dashed box marks the third bunch. (b) The third electron bunch areal density 
, in which the red dashed circle represents the region of 
. (c) The background color image represents the time evolution of the third bunch electron energy spectrum inside the red dashed circle of (b). The final energy spectrum of the third electron bunch is represented by the solid red curve. The black dashed line represents the prediction of the electron energy gain from 
. The initiation time of the acceleration serves as a variable parameter. (d) The cell-averaged electron divergence angle 
of the third bunch. All plots are derived from the simulation results at 
fs.
Fig. 6. Phase velocity 
analysis of reflected twisted beams. (a) The evolution of 
of three beams with different modes under the same initial conditions. The black dashed curve represents 
with the 
mode. The solid blue curve represents 
with the 
mode. The red dashed curve is the analytical prediction for 
of the reflected beam. (b) Evolution of the longitudinal electric field 
on the axis with 
. The solid black contours represent 
, while the red dashed curve is identical to that in (a).
Fig. 7. Electrons in the long-term trajectory, where the trajectory’s color represents the energy. (a) The trajectories of electron off-axis distance 
with 
, which are randomly selected from the third bunch that is situated close to the beam axis at 
fs. (b) The variation of electron trajectories off-axis distance with 
, selected from the third bunch with the condition that energy is less than 150 MeV at 
fs. (c) The trajectories of randomly selected electrons from the Figure 5(b) high-density region.
Table 1. 3D PIC simulation parameters.
is the critical density corresponding to the laser wavelength 
. The initial temperatures for electrons and ions are set to zero.View tableView in ArticleTable 1. 3D PIC simulation parameters.
is the critical density corresponding to the laser wavelength . The initial temperatures for electrons and ions are set to zero.Parameters for circularly polarized Gaussian laser Normalized amplitude ${a}_0=20$ Wavelength ${\lambda}_0=0.8\; \mu \mathrm{m}$ Pulse duration (Gaussian shape envelope) ${\tau}_{\mathrm{g}}=20$ Focal spot size ${w}_0=3\;\mu \mathrm{m}$ Location of the focal plane $x=0\;\mu \mathrm{m}$ Laser propagation direction $-x$ Circular polarization index $\sigma =+1$ Other simulation parameters Position of the foil and the wire –1.6 μm ≤ x ≤ 0 μm and 0 μm < x ≤ 1.6 μm Length and radius of wire ${L}_0=1.6\;\mu \mathrm{m},\ {R}_0=0.1\;\mu \mathrm{m}$ Electron and ion ( ${\mathrm{C}}^{6+}$ ${n}_{\mathrm{e}}=120.0{n}_{\mathrm{c}}$ ${n}_{\mathrm{i}}=20.0{n}_{\mathrm{c}}$ Simulation box ( $x\times y\times z$ 20.48 μm × 20.48 μm × 20.48 μm Cell number ( $x\times y\times z$ 1024 cells × 1024 cells × 1024 cells Macroparticles per cell for electrons 200 at $x\ge -0.95\;\mu \mathrm{m}$ $x<-0.95\;\mu \mathrm{m}$ Macroparticles per cell for ${\mathrm{C}}^{6+}$ 20
Tools
Get Citation
Copy Citation Text
Xiang Tang, Juexuan Hao, Yin Shi. Electron injection and acceleration in a twisted laser driven by the light fan[J]. High Power Laser Science and Engineering, 2024, 12(6): 06000e86
Paper Information
Category: Research Articles
Received: Apr. 23, 2024
Accepted: Aug. 21, 2024
Published Online: Jan. 3, 2025
The Author Email: Yin Shi (shiyin@ustc.edu.cn)
© Copyright 2018-2021 | Chinese Laser Press.
All Rights Reserved 沪ICP备15018463号-20