Direct simulation Monte Carlo of single-shot coherent Rayleigh-Brillouin scattering

A better understanding of the gas heating mechanism of industrial plasma sources is critical to the advancement of plasma processing technology. Coherent Rayleigh Brillouin scattering (CRBS) is a non-intrusive technique that measures the translational temperature of gas particles with atomic and molecular polarizability. In order to achieve a shorter measurement time, single-shot CRBS uses a chirped laser, allowing for a variation of the optical lattice wave frequency that results in probing the entire velocity distribution function (VDF) in a single laser shot measurement (~200 ns duration). We developed a direct simulation Monte Carlo (DSMC) code that accounts for a chirped optical lattice, which is validated with single-shot CRBS measurements. Overall, the simulation results are in good agreement with experimental data. However, the CRBS signal shape obtained from the DSMC simulation shows asymmetries and skewness of the Brillouin peaks when the chirp rate is fast. We will discuss the effects of the laser chirp rate on the CRBS signal.