Demonstration of an optical mixing technique to drive Kinetic Electrostatic Electron Nonlinear waves in laser produced plasmas

Abstract

A nitrogen gas Raman cell system has been constructed to shift a 70 J 527 nm laser beam to 600 nm with 20 J of energy. The 600 nm probe and a 200J, 527 nm pump beam were optically mixed in a laser produced (gas jet) plasma. The beating of the two laser beams formed a ponderomotive force that can drive Kinetic Electrostatic Electron Nonlinear (KEEN) waves discovered in Vlasov-Poisson simulations by Afeyan et al [1,2]. KEEN waves were detected in these experiments where traditional plasma theory would declare there to be a spectral gap (ie no linear waves possible). The detection was done using Thomson scattering with probe wavelengths of both 351 nm and 263.5 nm.