Light scattering measurements of energy partitioning in laser air sparks

Laser light scattering provides a powerful diagnostic of plasmas and fluids in the form of Thomson and Rayleigh scattering1. In this work, we present time and space resolved collective Thomson scattering measurements of T_e and n_e in the plasma core of atmospheric pressure air sparks generated with a 10ns pulse, 1064nm Nd:YAG laser. In the shockwave region, a combination of Rayleigh scattering and Filtered Rayleigh scattering are used to spatially and temporally resolve temperature, radial velocity and density. Filtered Rayleigh scattering is a technique whereby scattered light is spectrally filtered by an atomic or molecular gas to indirectly extract line shape information. These measurements cover a laser energy range of 30mJ to 100mJ and a temporal duration of 1-5μs after spark formation.