Assessment of Laser Induced Ablation Spectroscopy (LIAS) as a method for quantitative in situ surface diagnostic in plasma environments

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This work investigates Laser Induced Ablation Spectroscopy (LIAS) as an in situ diagnostic tool for fusion reactors and experiments. LIAS utilizes an intense laser pulse to ablate material during plasma operation, with ablation products penetrating the plasma's edge, where they are excited and ionized, leading to additional molecular dissociation. The emitted line radiation is captured using radiometrically calibrated spectroscopy. Results are presented for W/C/Al/D-mixed layers and amorphous hydrocarbon layers. A fast camera system enables time-resolved measurements of the LIAS process, revealing that 90% of the LIAS light from Tungsten is observed within 10±3 μs post-laser pulse, while carbon emissions peak within 20±3 μs. The study demonstrates the temporal separation of LIAS and LIBS emissions, facilitating distinct analyses in future experiments. The inverse photon efficiency for Balmer Dα-emission from a-C:D layers is calculated. Plasma perturbation due to LIAS is examined through variations in laser energy density, showing increased local perturbation with higher energy. A simple analytical model for local plasma perturbation during LIAS is introduced, revealing stronger effects from tungsten ablation than carbon. A Monte Carlo code models neutral atom emission profiles, showing good agreement in homogeneous plasma but discrepancies in emission shapes, indicating non-atomic species may significantly influence observed e