Generation of high quality electron beams from a quasi-phase-stable cascaded laser wakefield accelerator with density-tailored plasma segments

By controlling electron injection into the second period of the laser-driven wakefield in a downward density ramp, a high-quality low-energy electron beam can be accelerated in a short segment of high-density plasma. After a second downward density ramp followed by a low-density plasma plateau, the pre-accelerated electron beam can be seeded into the first period of the laser-driven wakefield for cascaded acceleration at an optimized phase. A monoenergetic electron beam with peak energy of ∼1.2 GeV can be generated from plasma with a length of 12 mm and density of 9 × 10 17 cm −3 , driven by a laser pulse with peak power of 77 TW. By modifying the acceleration stage comprising several density-ascending plasma segments, the peak energy of the quasi-monoenergetic electron beam can be efficiently increased by about 50% via a quasi-phase-stable multiple-cascade acceleration scheme.