Electron injection for direct acceleration to multi-GeV energy by a Gaussian laser field under the influence of axial magnetic field

Abstract

Electron injected in the path of a circularly polarized Gaussian laser beam under the influence of an external axial magnetic field is shown to be accelerated with a several GeV of energy in vacuum. A small angle of injection δ with 0∘<δ<20∘ for a sideway injection of electron about the axis of propagation of laser pulse is suggested for better trapping of electron in laser field and stronger betatron resonance under the influence of axial magnetic field. Such an optimized electron injection with axial magnetic field maximizes the acceleration gradient and electron energy gain with low electron scattering.

Phase space consideration of low energy electron injection for Direct Laser Acceleration

“…The optimum conditions for injection of high-energy electrons for the DLA are well discussed [11][12][13][14][15][16][17][18][19][20][21][22]. It has been noted that the energy gain obtained by electron depends on the phase of the laser field it has been injected into [19,21].…”

“…Rigorous theoretical analyses for the specific DLA models have shown that the energy gain depends specifically on the relative phase of the laser radiation and the Eugen electron's oscillation in the plasma channel [11][12][13]. Besides of the injection phase, the optimal initial electrons' energies have been also analysed [12][13][14][15][16][18][19][20][21][22]. Role of the electron transverse energy in the * starodubtceva.em19@physics.msu.ru acceleration was demonstrated analytically [12] and the results [14,16,18,19] indicated that the optimal electron's injection condition corresponds to a quite large value of its transverse energy: p 0⊥ /mc ≈ (4 ÷ 6) (melectron mass, c -speed of light).…”

“…Here and below ⊥ and notation indicate the direction perpendicular or parallel to laser radiation propagation direction, respectively. Several works have also demonstrated an importance of the electron initial longitudinal momentum for acceleration [18,22]. In [22] it was highlighted that electrons are accelerated most efficiently when injected at small angels to the plasma channel axis: p 0⊥ /p 0 ≈ (0.15 ÷ 0.40).…”

“…Several works have also demonstrated an importance of the electron initial longitudinal momentum for acceleration [18,22]. In [22] it was highlighted that electrons are accelerated most efficiently when injected at small angels to the plasma channel axis: p 0⊥ /p 0 ≈ (0.15 ÷ 0.40). All mentioned results demonstrate the possibility of an efficient energy gain by already pre-accelerated electrons.…”

Electron Acceleration by a Radially Polarized Laser Pulse in an Azimuthal Magnetic Field

“…A resonance occurs between the electrons and the electric field of the laser if we apply an intense magnetic field in the direction of laser pulse propagation [12]. A small angle of injection for a sideway injection of electron about the axis of propagation of laser pulse is suggested for better trapping of electron in laser field and stronger betatron resonance under the influence of axial magnetic field [13][14][15][16][17].…”