Bayesian optimization of massive material injection for disruption mitigation in tokamaks

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Název: Bayesian optimization of massive material injection for disruption mitigation in tokamaks
Autoři: Pusztai, Istvan, 1983, Ekmark, Ida, 1998, Bergström, H., Halldestam, P., Jansson, Patrik, 1972, Hoppe, M., Vallhagen, Oskar, 1997, Fülöp, Tünde-Maria, 1970
Zdroj: Skenande elektroner i fusionsplasmor Implementation of activities described in the Roadmap to Fusion during Horizon Europe through a joint programme of the members of the EUROfusion consortium Journal of Plasma Physics. 89(2)
Témata: runaway electrons, fusion plasma, plasma simulation
Popis: A Bayesian optimization framework is used to investigate scenarios for disruptions mitigated with combined deuterium and neon injection in ITER. The optimization cost function takes into account limits on the maximum runaway current, the transported fraction of the heat loss and the current quench time. The aim is to explore the dependence of the cost function on injected densities, and provide insights into the behaviour of the disruption dynamics for representative scenarios. The simulations are conducted using the numerical framework Dream (Disruption Runaway Electron Analysis Model). We show that, irrespective of the quantities of the material deposition, multi-megaampere runaway currents will be produced in the deuterium-tritium phase of operations, even in the optimal scenarios. However, the severity of the outcome can be influenced by tailoring the radial profile of the injected material; in particular, if the injected neon is deposited at the edge region it leads to a significant reduction of both the final runaway current and the transported heat losses. The Bayesian approach allows us to map the parameter space efficiently, with more accuracy in favourable parameter regions, thereby providing us with information about the robustness of the optima.
Popis souboru: electronic
Přístupová URL adresa: https://research.chalmers.se/publication/535373
https://research.chalmers.se/publication/535373/file/535373_Fulltext.pdf
Databáze: SwePub
Popis
Abstrakt:A Bayesian optimization framework is used to investigate scenarios for disruptions mitigated with combined deuterium and neon injection in ITER. The optimization cost function takes into account limits on the maximum runaway current, the transported fraction of the heat loss and the current quench time. The aim is to explore the dependence of the cost function on injected densities, and provide insights into the behaviour of the disruption dynamics for representative scenarios. The simulations are conducted using the numerical framework Dream (Disruption Runaway Electron Analysis Model). We show that, irrespective of the quantities of the material deposition, multi-megaampere runaway currents will be produced in the deuterium-tritium phase of operations, even in the optimal scenarios. However, the severity of the outcome can be influenced by tailoring the radial profile of the injected material; in particular, if the injected neon is deposited at the edge region it leads to a significant reduction of both the final runaway current and the transported heat losses. The Bayesian approach allows us to map the parameter space efficiently, with more accuracy in favourable parameter regions, thereby providing us with information about the robustness of the optima.
ISSN:00223778
14697807
DOI:10.1017/S0022377823000193