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  • 2025

    Abstract

    Magnetic fluctuations affecting turbulence and transport, which are manifest at finite normalized plasma pressure β, pose a significant challenge to magnetic confinement fusion devices aiming to achieve high performance. Such regimes are not yet comprehensively understood in stellarator geometry. This work presents simulations of electromagnetic instabilities and high-β turbulence in the Wendelstein 7-X (W7-X) stellarator, showing how ion-temperature-gradient-driven (ITG) turbulence is enhanced by unconventional kinetic ballooning modes well below the ideal MHD threshold. These sub-threshold KBMs (stKBMs) become strongly excited in the turbulent state and enable higher fluxes via zonal-flow erosion. The threshold of stKBM impact on turbulent fluxes is heavily dependent on the pressure gradient, evidenced here by the enhanced destabilization and fluxes resulting from the inclusion of an electron temperature gradient. Understanding and controlling these stKBMs will be paramount for W7-X and potentially other stellarators to achieve optimal performance.


    • Book : 65(1)
    • Pub. Date : 2025
    • Page : pp.016022
    • Keyword :
  • 2025


    • Book : 229()
    • Pub. Date : 2025
    • Page : pp.112418
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  • 2025


    • Book : 431()
    • Pub. Date : 2025
    • Page : pp.113717
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  • 2025


    • Book : 604()
    • Pub. Date : 2025
    • Page : pp.155452
    • Keyword :
  • 2025

    Abstract

    The advent of machine learning (ML) has revolutionized the research of plasma confinement, offering new avenues for exploration. It enables the construction of models that effectively streamline the simulation process. While previous first-principles simulations have provided physics-based transport information, they have been inadequate fast for real-time applications or plasma control. In order to address this challenge, we introduce SExFC, a surrogate model based on the Gyro-Landau Extended Fluid Code (ExFC). An approach of physics-based database construction is detailed, as well the validity is illustrated. Through harnessing the power of ML, SExFC offers the capability to deliver rapid and precise predictions, facilitating real-time applications and enhancing plasma control. The proposed model integrates the recurrent neural network (RNN) algorithm, specifically leveraging the Gated Recurrent Unit (GRU) for iterative prediction of flux evolutions based on radial profiles. Therefore, the SExFC model has the potential to enable rapid and physics-based predictions that can be seamlessly integrated into future real-time plasma control systems.


    • Book : 65(1)
    • Pub. Date : 2025
    • Page : pp.016015
    • Keyword :
  • 2025


    • Book : 25(1)
    • Pub. Date : 2025
    • Page : pp.04024310
    • Keyword :
  • 2025


    • Book : 197()
    • Pub. Date : 2025
    • Page : pp.112429
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  • 2025


    • Book : 112()
    • Pub. Date : 2025
    • Page : pp.397-410
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  • 2025


    • Book : 202()
    • Pub. Date : 2025
    • Page : pp.110606
    • Keyword :
  • 2025


    • Book : 212()
    • Pub. Date : 2025
    • Page : pp.111046
    • Keyword :