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
¹⁸
W/cm
²
into underdense helium plasma at a density of 𝓃
_e
≤ 5 × 10
¹⁹
cm
^-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.