Role of shock-front and ionization in self-injecion of laser-plasma acceleration.
Palla D., Baffigi F., Brandi F., Fulgentini L., Koester P., Labate L., Londrillo P, Gizzi L.A.
In the Laser Wake Field Accelerator (LWFA), an ultra-intense laser pulse is used to produce a plasma wave (wakefield). The high longitudinal electric field supported by the plasma wave is used to accelerate trapped (self-injected) electrons with velocity close to the wave phase velocity. With respect to the standard RF-linacs, the accelerating gradient of LWFA is much higher and the acceleration length is 1000 time shorter. A critical aspect of LWFA is the self-injection mechanism itself which can strongly influence the quality (energy, monochromaticity, emittance) of the acceleration process. We explored the effect of shock-front injection and ionization on the injection via numerical simulations and experiments. Our study shows improvement in both beam quality stability of the process.