Verification of Multistage Particle Acceleration by Laser Beat-waves

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The purpose of this project is to verify multistage laser acceleration feasibility using an ultra short pulse laser, which is to after-accelerate MeV electrons once accelerated by the laser-beat-wave. Soin the past two years, we have mainly constructed an ultra-short pulse high intensity laser system.In the first year (1995), we have demonstrated electron accelerations of a few hundred keV accompanied with a CO_2 laser backward Raman scattering. Thus accelerated high energy electrons are the seed electrons to be injected into the laser accelerator, either beat-wave or wakefield one. By YAG laser Thomson scattering, we have measured both temporally and spatially resolved spectrum of beat-wave excited relativistic plasma waves. We have started to construct a short pulse glass laser system for after-acceleration of electrons.In the second year (1996), we have modified the Gekko MII glass laser system to short pulse laser. We have changed the front end to Ti : Sapphire oscillator and regenerative amplifier combination system. At the output of the final spatial filter we put a pulse compression grating pair. The completed system produces 25J in 0.7ps or 35TW.Now we are doing a solid target illumination, where high enegy ion and neutron are detected. Soon we will do gas-jet experiment, in which the wakefield will be excited and electrons will be accelerated.