Abstract Using plasma mirror injection we demonstrate, both analytically and numerically, that a circularly polarized helical laser pulse can accelerate highly collimated dense bunches of electrons to several hundred MeV using currently available laser systems. The circularpolarized helical (Laguerre–Gaussian) beam has a unique field structure where the transverse fields have helixlike wavefronts which tend to zero onaxis where, at focus, there are large onaxis longitudinal magnetic and electric fields. The acceleration of electrons by this type of laser pulse is analyzed as a function of radial mode number and it is shown that the radial mode number has a profound effect on electron acceleration close to the laser axis. Using threedimensional particleincell simulations a circularpolarized helical laser beam with power of 0.6 PW is shown to produce several dense attosecond bunches. The bunch nearest the peak of the laser envelope has an energy of 0.47 GeV with spread as narrow as 10%, a charge of 26 pC with duration of ∼ 400 as, and a very low divergence of 20 mrad. The confinement by longitudinal magnetic fields in the nearaxis region allows the longitudinal electric fields to accelerate the electrons over a long period after the initial reflection. Both themore »
This content will become publicly available on December 1, 2023
Electron acceleration from transparent targets irradiated by ultraintense helical laser beams
Abstract The concept of electron acceleration by a laser beam in vacuum is attractive due to its seeming simplicity, but its implementation has been elusive, as it requires efficient electron injection into the beam and a mechanism for counteracting transverse expulsion. Electron injection during laser reflection off a plasma mirror is a promising mechanism, but it is sensitive to the plasma density gradient that is hard to control. We get around this sensitivity by utilizing volumetric injection that takes place when a helical laser beam traverses a lowdensity target. The electron retention is achieved by choosing the helicity, such that the transverse field profiles are hollow while the longitudinal fields are peaked on central axis. We demonstrate using threedimensional simulations that a 3 PW helical laser can generate a 50 pC lowdivergence electron beam with a maximum energy of 1.5 GeV. The unique features of the beam are short acceleration distance (∼100 μm), compact transverse size, high areal density, and electron bunching (∼100 as bunch duration).
 Award ID(s):
 1903098
 Publication Date:
 NSFPAR ID:
 10335199
 Journal Name:
 Communications Physics
 Volume:
 5
 Issue:
 1
 ISSN:
 23993650
 Sponsoring Org:
 National Science Foundation
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