Fabrication of three-dimensionally structured plasma waveguide and application to induction of electron injection and betatron oscillation in a laser wakefield electron accelerator

By adding a transverse heater pulse with controlled intensity distribution into the axicon ignitor-heater scheme for optically producing a plasma waveguide, three-dimensionally structured plasma waveguide can be fabricated. The additional heater pulse generates further heating of the plasma filament produced by the axicon pulses in a spatially and temporally controlled manner. The succeeding evolution of the plasma leads to a properly structured plasma waveguide that suits for targeted application. With this technique, induction of electron injection in a plasma-waveguide-based laser wakefield accelerator was achieved and resulted in production of a quasi-monoenergetic electron beam with an electron energy reaching 280 MeV and an energy spread as low as 1% in a 4-mm-long gas jet by properly setting the transverse heater pulse delay with respect to the axicon pulses. Furthermore, strong hard X-ray beam was observed upon further increase of transverse heater delay so that the irradiated section in the plasma waveguide acts as a plasma kicker to enhance betatron oscillation.