Expansion Dynamic and Characterization of Stagnation Layer in Laterally Colliding Plasmas: Dependence of Observation Bandwidth and Plasma Plume Separation

Abstract

The colliding laser-produced plasma (CLPP) has a wide range of applications in various contexts, that might start with astrophysical applications or pulsed laser deposition or Laser-Induced Breakdown Spectroscopy (LIBS), which is a powerful analytical technique for elemental analysis and material identification. In CLPP experiments, the stagnation layer might form at the interface region when two dense laser-induced plasmas collide, and the degree of stagnation can be diagnosed by the collisionality parameter that is used to determine what kind of interaction will take place, i.e., soft or hard stagnation. Our experimental work presents the results of the temporal, spatial and semi-spectrally imaging of colliding plasmas of aluminium and silicon targets. The analysis is focused on describing the velocity of the expanding plasma front for the interaction zone. The aim of the work presented here is to further advance and study colliding plasma techniques, as well as other methods to realize and control species density and expansion, with a view to a deep understanding of these complex mechanisms and optimising emission in the visible wavelength range. All investigation sequences were based on a similar experimental setup, where two different focusing lenses were used with an effective focal length (EFL) of approx. 100mm or 125mm to achieve seed separation around 1.66mm or 2.16mm, respectively. Time-resolved emission imaging was employed to track the stagnation layer‛s size and shape, which might act as a signature of hard versus soft stagnation. The study provides a considerable amount of detailed data related to the expansion velocity of the interaction zone which extends the understanding of the behaviour of particular species within colliding laser-produced plasmas.

Featurization of Ultrafast Expansion and Geometrical Properties of Heterogeneous Colliding Plasmas

“…A detailed description of the digital nanosecond imaging architecture of colliding laser-produced plasma can be found it in Refs. [5,3]. Figure 1 explains the temporal evolution example of the Si-Al stagnation layer and its related features using a bandpass filter 450 nm.…”

“…The effect of the atomic mass of the ablating target on the formation and expansion of the interaction region in laterally colliding plasmas has been focused on many scientific contributions, where several techniques and setups were applied to achieve colliding laser-produced plasmas of different elements [1][2][3][4]. Some reasons behind these studies focused on the possibility to enhance specific emission lines from one of the dual materials by introducing the presence of the other target material or used the outcomes for particular applications of nanocomposites, additionally, investigated the plume-front velocity in different environments as well as the effect of the different surrounding media on the electron density and its temperature.…”