EuroPED-NN: uncertainty aware surrogate model

• Published in: Plasma physics and controlled fusion 2024-09, Vol.66 (9), p.95012
• Main Authors: Panera Alvarez, A, Ho, A, Järvinen, A, Saarelma, S, Wiesen, S
• Format: Article
• Language: English
• Subjects: artificial intelligence; Bayesian neural network; machine learning; nuclear fusion; pedestal; uncertainty
• ISSN: 0741-3335; 1361-6587
• DOI: 10.1088/1361-6587/ad6707

This work successfully generates an uncertainty-aware surrogate model of the EuroPED plasma pedestal model using the Bayesian neural network with noise contrastive prior (BNN-NCP) technique. This model is trained using data from the JET-ILW pedestal database and subsequent model evaluations, conforming to EuroPED-NN. The BNN-NCP technique has been proven to be a suitable method for generating uncertainty-aware surrogate models. It matches the output results of a regular neural network while providing confidence estimates for predictions as uncertainties. Additionally, it highlights out-of-distribution regions using surrogate model uncertainties. This provides critical insights into model robustness and reliability. EuroPED-NN has been physically validated, first, analyzing electron density n e ( ψ pol = 0.94 ) with respect to increasing plasma current, I p , and second, validating the Δ − β p , ped relation associated with the EuroPED model. This affirms the robustness of the underlying physics learned by the surrogate model. On top of that, the method was used to develop a EuroPED-like model fed with experimental data, i.e. an uncertainty aware experimental model, which is functional in JET database. Both models have been also tested in ∼50 AUG shots.