Experimental study of fs electron bunch generation by laser plasma cathode

Plasmas irradiated by intense short laser pulses can be an efficient, compact, and flexible source of multi-MeV electrons constituting a bunchwith its duration in the femtosecond range. So we have studied a laser plasma cathode based on Laser Wake Field Acceleration (LWFA) with electron injection by wave-breaking, which is driven by a femtosecond intense laser pulse (Ti:Sapphire, max 12TW, lambda = 800nm , 50fs, 10Hz) tightly focused in supersonic helium gas-jet. The wave-breaking is the simplest way to inject energetic electrons into the wakes produced by an intense laser pulse. However, the wave-breaking requires a steep density plasmainterface with order of the plasma wavelength. According to our previous experiment, this condition can be produced via generation of a shock-wave in the gas jet by proper laser prepulse irradiation. It shows ejection of a narrow-cone MeV electron beam from a gas jet depend strongly on the prepulse contrast ratio. Furthermore, in case of higher gas density, the effect of laser prepulse become more sophisticate.The laser pulse is refracted at the edge of the cavity produced by the prepulse and thiseffect limit the narrow-cone MeV electron beam production of LWFA. In addition, I will also mention a narrow energy spread e-spectrum obtained in our recent experiment, development of a shockwave-free supersonic gas jet and gas filled capillary discharge wave-guide.11th Advanced Accelerator Concept 200