Wakefield excitation and electron injection using multiple laser pulses in plasmas

Efficient excitation of large amplitude, relativistic plasma waves and the production of high quality (low energy spread and low emittance) electron bunches is of fundamental importance to plasma-based accelerators and their applications. In this talk, several methods for wakefield excitation and laser-triggered injection of high quality electron bunches that rely on one or more laser pulses will be discussed. Novel techniques for exciting and controlling the laser-induced wakefields using multiple, multi-color pulses and pulse trains will be presented. In addition, an electron injection method that relies on two-color ionization injection will be discussed. Here a low frequency, high normalized vector potential pulse is used to drive the wakefield, and a trailing high frequency, low normalized vector potential (but high electric field) pulse is used for ionization injection. This injection mechanism is compared to self-trapping in the nonlinear bubble regime, in which the trapping threshold dependence on laser intensity and wake phase velocity has been numerically explored.