Figure 1
From: Direct acceleration of electrons by a CO2 laser in a curved plasma waveguide
Sketch of direct laser acceleration of electron in a CPW.
(a) A linearly polarized CO2 laser and a relativistic electron beam are injected into a CPW from the left side. The electrons located in the right phase can be accelerated by the TM modes, resulting in the generation of a chain of energetic ultrashort electron bunches (right exit of CPW). (b–d) Shows the longitudinal electric field and electron motion at different propagating distances (marked by the red cube-frame in (a)), where a quarter of Ex field are removed to avoid overlapping and the electron energy is presented by the color. The figure on the back and left walls in (b–d) presents the Ex field and electron position (black dots) at longitudinal slice z = 0 and transverse cross-section x = 6.5λ0, respectively. The waveguide is properly designed with a curvature in the polarization direction, detail dimension of half of the CPW period is shown in (e) for x-y plain (the waveguide is uniform along z-direction and the size in z dimension is 12λ0 in the presented 3D PIC simulation). The l1 is the half-CPW curvature period and the ratio of l1 and l2 is optimized according to the simulation (l2 = 0.442l1). If l1 matches the dephasing length, the electron bunch can continuously gain energy until it overtakes the entire laser pulse.
