A multi-model system-identification comparison with the global particle dynamics in TCV

Résumé fourni par la source

Abstract In this work, we compare physics-based dynamic exhaust models with frequency response measurements (FRMs) of the global particle dynamics in the Tokamak à Configuration Variable (TCV). The aim is to understand and model the experimental in-vessel dynamic response of plasma and neutrals to deuterium gas puff modulations with three models of varying fidelity: a 0D three chamber model (TCM); DIV1D, which models the edge plasma in 1D, and SOLEDGE3X for 2D-axisymmetric modeling. We find that the dynamic behavior of the global particle balance as observed in TCV can be reproduced by SOLEDGE3X and with specific parameter settings also by TCM and DIV1D, for FRMs between 3 and 40 Hz. For TCM and DIV1D, the coupling to a core reservoir and a realistic time for neutrals to ionize are found important to align with measurements. We argue from this comparison that for dynamics driven by particle kinetics, it is almost impossible to investigate one domain irrespective of others and that one should formally consider the coupled nature of the particle dynamics over domains. In TCV, this means that one cannot ignore that over 60% of the neutral ionization takes place inside the core confined region, for the scenarios considered in this study. The presented dynamic model validation should be detailed much further and extended to other devices to better understand exhaust dynamics, providing the essential building blocks required to design exhaust control systems in future fusion reactors.

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