Ponderomotive electron scattering from high-intensity laser pulses

With the increasing number of petawatt laser systems being developed worldwide, and laser intensities now surpassing the 1E23W/cm^2 barrier, we are entering a new regime of laser-plasma interactions. However, a direct measurement of these extreme laser intensities has yet to be made and is currently only inferred from indirect methods. An open question remains: how can we determine directly the peak intensity of a high-power, high-intensity laser system?

In this work we report on two recent experiments to measure ponderomotive electron scattering from Nitrogen and Argon gas at pressures of 1E-4mBar as a potential way to determine the peak laser intensity and characteristics of the focal spots. The first experiment was performed at the CLPU laser facility in Salamanca, Spain where the 1PW VEGA3 laser system was focused to an intensity roughly around 1E20W/cm^2 using an f/10 optic. The second experiment was performed with the Scarlett laser facility at The Ohio State University operating around 180TW where the peak intensity was varied between 1-10E20W/cm^2 using f/2 to f/6 apodizers.

Measurements of the scattered electron distributions using a variety of diagnostics are compared to analytic theory and Monte Carlo simulations.