Simulations of laser-wakefield acceleration with external electron bunch injection for REGAE experiments

Laser-wakefield acceleration has experienced growing scientific interest and fast development during the last decade. Short and highly intense laser pulses focused into a gas target, ionise the gas and may excite large amplitude, co-propagating plasma waves that support extreme electric fields (>10 GV/m) for acceleration of charged particles. These fields are orders of magnitude larger than in conventional radio-frequency accelerators. The REGAE facility at DESY offers the unique possibility to study the external injection of pre-accelerated electron bunches from a stable and fully controlled conventional accelerator, and their subsequent acceleration in plasma wakefields. A set of 2- and 3-dimensional numerical simulations was performed with the particle-in-cell code OSIRIS, showing a wide variety of effects which will be possible to explore in the future with REGAE, which provides 2-5 MeV electron bunches of 10 femtosecond length. Topics of particular interest are: probing of the electric wakefields, emittance evolution, bunch compression, and controlled betatron radiation emission.