Beat‐wave experiments at Ecole Polytechnique

We summarize the results obtained in the context of the beat‐wave experiments performed at Ecole Polytechnique in France. We first study the generation of long and homogeneous plasmas by multiphotoionization of low density gases and observe the density variation with time due to the ponderomotive force of the ionizing laser beam. In the Nd‐laser beat‐wave experiments we observe in the resonant conditions the generation of intense electron plasma waves. We also measure some daughter ion and electron waves generated by the decay of these primary electron waves by modulational instability (coupling with ion motions). These results show the importance of the ion hydrodynamic for the generation and the evolution of the accelerating electric fields in beat‐wave experiments.