Nonlinear Electron Plasma Waves
The dynamics of strongly driven electron plasma waves (EPW’s) is a rich area of plasma physics that involves many complex phenomena that are difficult to predict in simulations or diagnose experimentally. As an electron plasma wave is driven to high amplitude, a multitude of effects can occur such as nonlinear frequency shifts, wave breaking, acceleration of high-energy electrons, and cascading to shorter-wavelength plasma waves.
Experiments are carried out that focus on probing nonlinear EPW dynamics in the underdense plasma (UDP) target chamber of the MTW laser. To control the amplitude of the EPW’s, two counter-propagating laser pulses (pump and seed), whose frequency difference equals the plasma frequency, are being developed. The pump pulse will be provided by the current 1053-nm, 25-ps, 75-J MTW laser and the seed pulse will be provided by the ultrashort OPAL, which will deliver 50 mJ in 50 fs with a central wavelength tunable from 1100 nm to 1300 nm. To measure the plasma conditions and probe the amplitude and frequency of the driven electron plasma wave, optical Thomson scattering is used [3].