Electron source produced in the self-modulated laser wake field regime

ABSTRACT In this article, we report on experimental electron spectra generated by SMLWF in the ultra-relativistic regime a>1,where a0 is the normalized vector potential of the laser. For the first time, we have observed that in our range of parameters themaximum electron energy increases when the electron density decreases. A maximum of 70 MeV was observed for n/n1 .5%.1. INTRODUCTION Laser plasma interaction in the relativistic regime is crucial for laser plasma acceleration 13 and for Inertial Confinement Fusion(ICF) with the fast ignitor scheme . The success of these applications depends on the efficient transfer of energy from the laserto electrons. Electrons are trapped in high amplitude relativistic plasma waves (RPW) driven by the Self-Modulated Laser WakeField instability (SMLWF) In this relativistic regime plasma waves can reach amplitude of a few tens of percent 810,accelerating electrons to energies of several tens MeV1 1,12 Various mechanisms, such as relativistic effects and ponderomotiveself-channel4ing13 must be taken into account in estimating the maximum electron energy. On the other hand, the measurement ofmulti-MeV electrons was imputed to direct laser acceleration in a plasma channel14, and the effective temperature deduced fromelectron spectra was observed to grow with electron density 15•