Investigations on the effect of target angle on the stagnation layer of colliding laser produced plasmas of aluminum and silicon

The temporal and spatial characteristics of two colliding laser produced plasmas are investigated over a range of flat to wedge-shaped targets for aluminum and silicon. Fast-gated visible photography was used to investigate how the length and width of the stagnation evolved over timescales from 300 to 500 ns with filters used to help to separate the emission from neutral and higher ionization states. The velocity of the stagnation layer was measured to be in the range of 3.8 - 6.6 x 10 6 cm/s. The length of the stagnation layer was observed to increase as the wedge angle decreased from 180 & DEG; to 80 & DEG;. Time-resolved spectra were also recorded, which helped to reveal the dominant ion stage in a given time interval. Based on this analysis, the longest and most homogenous stagnation layers appear to be comprised of mostly neutral and singly ionized species. Line widths were used to estimate electron densities of 1 x 10 17 cm - 3 and temperatures of 1.9-2.1 eV, which remained fairly constant over the timescales observed. The analysis suggests that there is significant collisional reheating of the stagnation layer followed by radiative recombination and that the stagnation layer dynamics are not sensitive to small changes in mass. (C) 2021 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).