Optically produced collimated quasimonoenergetic electron beams for laser-plasma acceleration

Plasma-based electron accelerators offer a promising way in the development of the particle acceleration techniques. Acceleration gradients achievable in a laser wakefield are several orders of magnitude higher than in conventional electron accelerators, paving the way to table top electron accelerators suitable for various applications in science, medicine, and diagnostics. One of the key problems in the laser-wakefield electron acceleration is the problem of injection of electrons in a plasma wave. At high laser intensity (I>10¹⁸ W/cm²) excited wakefield amplitude can be sufficient to trap electrons from cold background plasma, however in this regime the acceleration is a highly nonlinear process leading to high instability of resulting energy, charge and direction. Many attempts have been made to make the process more reliable, however the problem has not been solved yet. The trapping issue is especially crucial when the excitation of a plasma wake occurs in more stable and reproducible linear regime. In the present work we have investigated experimentally generation of collimated quasimonoenergetic bunches of electrons by focusing intense femtosecond laser radiation on the edge of aluminum foil which can be further used for injection into a laser produced plasma wake.