High-energy electron generations by a high power laser and a density-tapered gas cell

Summary form only given. High energy electrons can be produced by the laser wakefield acceleration (LWFA), where the electrons are accelerated by a strong longitudinal electric field generated by a high power laser pulse and a plasma. In this case, the dephasing problem, which occurs due to the velocity difference between the accelerated electrons and the propagating plasma wave, is one of the most important energy saturation factors in LWFA. In this presentation, we show that the dephasing problem can be mitigated by a density-tapered gas cell, where the two velocities are matched. So far we have developed such a density-tapered gas cell and used it for laser wakefield acceleration experiments. The 20 TW Ti:sapphire laser in our laboratory was used for the experiments and the results show that the electron beam energies are significantly enhanced by the density-tapered gas cell. In this presentation, we show the detailed experimental and particle-in-cell simulation results.