Measurement of Forward Raman Scattering and Electron Acceleration from High-Intensity Laser--Plasma Interactions at 527 nm

High-intensity laser-plasma interaction experiments were performed using high-power laser pulses (greater than 8 TW) at a wavelength of 527 nm. These pulses were focused to intensity greater than [10.sup.18] W/[cm.sup.2] into underdense helium plasma at a density of [n.sub.e] [is less than or equal to] 5 x [10.sup.19] [cm.sup.-3]. Systematic examination of the forward Raman scattering instability was performed by measuring the spectrum of the forward scattered light. It was found that the three-wave instability occurs first, which then proceeds to a nonlinear regime involving four-wave processes. Measurements of the accelerated electron spectrum suggest that higher phase velocity plasma waves are generated than when using lower frequency light. Index Terms--Electron accelerator, electromagnetic scattering by plasma media, plasma waves.