First STUD pulse experiments on controlling Resonantly excited electron plasma waves in high energy density plasmas.

Spike Trains of Uneven Duration and Delay (STUD pulses) are a promising means of controlling Laser Plasma Instabilities (LPI) by modulating the laser on the instability growth timescale. The nonlinear evolution of resonantly driven electron plasma waves involves disparate timescales: the plasma frequency, instability growth time, plasma wave walk-off time trapping time, wavebreaking time, and nonlinear self-organized phase-space-structure recurrence time. To optimize STUD pulses for LPI control, it is necessary to navigate between these various timescales. Using the high repetition rate, short pulse, petawatt laser system ALEPH at CSU, we have conducted the first STUD pulse optimization experiments of Resonance Absorption (RA) generated plasma waves and their control. 3358 shots were dedicated to the exploration of RA physics. We varied the angle between the 800 nm heater and interaction beams and their mutual delay, to change the density scalelength and plasma temperature. The amplitudes, durations, and delays between the 10 spike sequences were systematically varied and scattered spectra measured at 800, 400, 566, and 1600 nm. We will show the STUD pulse conditions that result in the largest stable plasma waves we could generate due to RA at n_c and Stimulated Rahman Scattering (SRS) at n_c /4.