The effect of blast wave re-focusing on a laser-induced plasma

Abstract

The effect of laser-induced plasma confinement on lifetime and temperature is reported using cylindrical reflectors. This is determined experimentally in a gas cell, with hydrogen as test gas, and cylindrical shock reflectors of different diameters. The temperature evolution of confined and unconfined laser-induced plasma has been measured using plasma emission spectroscopy. Temperatures were determined through the plasma line-to-continuum thermometry technique in the hydrogen Balmer series using the Hα and Hβ transitions at λ = 656 nm and λ = 486 nm, respectively. The experiments found that re-focusing the blast wave can significantly increase temperatures during the exponential decay of the plasma. The experimental results also show that confinement increases peak plasma temperatures, and that plasma lifetimes are only marginally affected by the confinement.