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The density shoulder represents a universal physical phenomenon that is closely related to the particle and energy transports occurring within the scrape-off layer (SOL) region of tokamak devices. A novel method has been developed to identify the density shoulder through the analysis of the bump structure in the time delay spectra from monostatic microwave reflectometry in EAST tokamak, obviating the need for density profile reconstruction. The density shoulder in EAST is characterized by a number of distinctive features. The density shoulder is mostly situated at a distance of 0–3 cm from the last closed flux surface, with a width of a few centimeters. No significant correlation is observed between its occurrence and the auxiliary heating or the confinement state. In the case of H-mode with quasi-coherent mode (QCM), a significant and positive correlation is observed between the density shoulder amplitude and QCM intensity. In the case of grassy-edge localized mode (ELM)-like H-mode, a density shoulder is also observed during the inter-ELM stage. Furthermore, as supersonic molecular beam injection (SMBI) deposits occur within the range of ρ = 0.9 ∼ 1, the density shoulder is also enhanced during the SMBI fueling process. Moreover, it appears that the neutral pressure has a more pronounced impact on the overall offset of the density profile than the strength of the density shoulder. These results collectively indicate that the outward particle transport from the pedestal to the SOL region plays a crucial role in the evolution of the density shoulder. [ABSTRACT FROM AUTHOR]

The impact of sample preparation on bitumen content measurement using LIBS was investigated by collecting spectra from wet and dry tailings. A multivariate data analysis model was developed using optimal wavelength selection for bitumen content classification and prediction in tailings. Wet tailings can be classified into three classes (low, medium, and high bitumen) with 12.1 % error, while dry tailings have a classification error of 6.1 %. Quantitative analysis showed a bitumen content prediction error of 4.7 % for wet tailings and 8.9 % for dry tailings. Wet tailings showed a 1.8–2.5 times improvement in the limit of detection range compared to dry tailings. Plasma density and crater size measurements revealed that plasma density fluctuation was 2.7 times lower in wet tailings due to consistent crater formation from laser-tailings interaction. The lower plasma density fluctuation indicates a stable mass ablation for wet samples, which is attributed as the primary reason for significant LIBS performance improvement on wet tailings. [Display omitted] • Optimization of multivariate calibration model for improved prediction accuracy of the bitumen measurement in using LIBS. • Bitumen measurement accuracy significantly improved in wet tailings compared to dry tailings. • Plasma density and laser-produced craters are substantially consistent for wet tailings. • Use of compact laser and developed calibration model are promising for the future advancement of portable LIBS. [ABSTRACT FROM AUTHOR]