Investigation of Plasma Gratings as a Diagnostic for Low Temperature Plasmas

Experimental characterization of the electron velocity distribution function (EVDF) at relevant

temporal and spatial scales remains a challenge for conventional laser diagnostics, such as

Thomson Scattering, due to low signal levels under typical low temperature plasma (LTP)

conditions. The present work aims to evaluate the potential utilization of scattering from

transient plasma gratings as a diagnostic for measuring spatially and temporally resolved EVDFs.

This work considers both the formation and decay of plasma gratings in non-magnetized LTPs

produced by pondermotive forcing in crossed femtosecond or picosecond pump beams.

The plasma grating dynamics are investigated using 1D1V kinetic simulations with a frozen ion

background. The spatiotemporal evolution of the EVDF is simulated in a semi-Lagrangian

framework with the BGK operator accounting for collisions in the weakly ionized plasma. Light

scattering from a temporally delayed probe beam is computed by numerical beam propagation

within the slowly varying envelope approximation. Numerical results are presented over a

range of plasma conditions, grating formation conditions, and scattering parameters as

characterized by key dimensionless parameters. These results further motivate the design of

experiments capable of realizing single shot characterization of the EVDF and other plasma

parameters.