ELECTRON ACCELERATION IN ND-LASER PLASMA BEAT-WAVE EXPERIMENTS

The beating between two colinear Nd-YLF (lambda = 1.053 mu m, tau = 90 ps) and Nd-YAG (lambda = 1.054 mu m, tau = 160 ps) lasers in a homoge neous plasma (n(c) = 10(17) cm(-3)) generates intense relativistic pla sma waves associated with a high longitudinal electric field of the or der of 1 GV m(-1). In the conditions of the experiment, these electron plasma waves couple with ion waves in the regime of modulational inst ability as it has been demonstrated by electric field amplitude and sa turation time measurements by Thomson scattering. When 3 MeV energy el ectrons are injected into the plasma, several hundreds of electrons ac celerated up to 3.7 MeV are observed in correlation with the Thomson s cattering signal associated to the plasma waves. This result is in agr eement with a numerical simulation which takes into account the relati ve focussing geometry of electron and laser beams.