Since the invention of laser wakefields, generated by high intensity, femtosecond pulses in gaseous targets, the electron acceleration in dilute plasmas has been investigated both theoretically and experimentally. This scheme looks extremely promising to partially replace the conventional accelerators and to generate high quality relativistic electron bunches reaching several GeV maximum energies. However, in the case of ultrashort pulses new physical effects emerge, which are not yet fully understood, or not explored in the literature. Since the propagation of ultrashort laser pulses in plasma is highly nonlinear, it is necessary to model the interaction by means of numerical simulations. With the help of such (particle-in-cell) simulations I studied the electron acceleration process driven by very short (few-cycle) pulses and identified several negative effects which are not so important (or not present) in the case of longer pulses. Based on the knowledge acquired in the last two years I designed a three-component target, which is suitable for very efficient electron acceleration and allows for high energy gain within 2-millimeter distance. In my talk I will present the theoretical description of the short-pulse propagation in the proposed millimeter-long, three-stage target and I will show that, theoretically, GeV-class electron bunches can be accelerated by a half-Joule laser pulse in this new scheme.
In the second part of my talk, I will briefly discuss the possibility of proton (or deuteron) acceleration from high density gas jets using ~ 100 mJ laser pulses, which is highly relevant to the SYLOS-2 laser installed at ELI ALPS. I will present a realistic 3D simulation which indicates that 1 MeV mono-energetic proton bunch can be generated by such ultra-short laser pulses at ~kHz repetition rate.