Spatial and temporal characterization of double-pulse laser-induced plasmas in the orthogonal geometry

abstract

English

Double-pulse laser-induced breakdown spectroscopy (DP-LIBS) is a promising approach to improve the common limitations of single-pulse LIBS. Naturally, the use of two lasers leads to more complicated plasma dynamics than the use of a single ablation pulse. Thus, we studied the temporal evolution of double-pulse laser-induced plasmas in the orthogonal geometry. Plasmas induced using both negative and positive inter-pulse delays (relative to the ablation pulse) are studied. Plasmas characterization is carried out in terms of their electron density, temperature, and volume with high temporal and spatial resolution. The spatial resolution is obtained using a tomography technique based on the Radon transformation. The tomographic reconstruction of the white-light emissivity of the plasmas yields information about their overall size. On the contrary, by using band-pass filters and carrying out the tomographic reconstruction of the filtered emissivity corresponds to the distribution of selected emitting species, e.g., atomic Cu. Lastly, the tomographic reconstruction of spectrally resolved images allows us to determine the spatial distribution of the electron density and temperature. According to our results, the pre-ablation geometry (negative interpulse delay) yields a more stable and uniform plasma compared to the plasmas induced in the re-heating (positive interpulse delay) geometry. Overall, our results provide a detailed overview of the mechanisms involved in DP-LIBS signal enhancement.

Laser-induced plasma, Laser-induced breakdown spectroscopy, Double-pulse laser-induced breakdown spectroscopy, Plasma tomography, Radon reconstruction

KÉPEŠ, E.; GORNUSHKIN, I.; POŘÍZKA, P.; KAISER, J.

21. 9. 2020