Enhanced Transport at High Plasma Pressure and Subthreshold Kinetic Ballooning Modes in Wendelstein 7-X
P. Mulholland, K. Aleynikova, B. J. Faber, M. J. Pueschel, J. H. E. Proll, C. C. Hegna, P. W. Terry, C. Nührenberg
Abstract
High-performance fusion plasmas, requiring high pressure β, are not well understood in stellarator-type experiments. Here, the effect of β on ion-temperature-gradient-driven (ITG) turbulence is studied in Wendelstein 7-X (W7-X), showing that subdominant kinetic ballooning modes (KBMs) are unstable well below the ideal MHD threshold and get strongly excited in the turbulence. By zonal-flow erosion, these subthreshold KBMs (stKBMs) affect ITG saturation and enable higher heat fluxes. Controlling stKBMs will be essential to allow W7-X and future stellarators to achieve maximum performance.
Topics & Concepts
StellaratorWendelstein 7-XBallooningPhysicsPlasmaTurbulenceMagnetohydrodynamicsPressure gradientKinetic energySubthreshold conductionAtomic physicsZonal flow (plasma)BETA (programming language)Nuclear fusionNuclear physicsMechanicsTokamakClassical mechanicsComputer scienceProgramming languageQuantum mechanicsVoltageTransistorMagnetic confinement fusion researchLaser-Plasma Interactions and DiagnosticsFusion materials and technologies