Gyrokinetic turbulence modeling of a high performance scenario in JT-60SA

Local gyrokinetic simulations are used to model turbulent transport for the first time in a representative high-performance plasma discharge projected for the new JT-60SA tokamak. The discharge features a double-null separatrix, 41 MW of combined neutral beam heating and electron cyclotron heating,...

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Bibliographic Details
Published in:Nuclear fusion 2024-02, Vol.64 (2), p.26005
Main Authors: Iantchenko, A., Pueschel, M.J., Brunner, S., Coda, S.
Format: Article
Language:English
Subjects:
fast ions
high
high β
JT-60SA
non-zonal transition
turbulence simulations
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Summary:Local gyrokinetic simulations are used to model turbulent transport for the first time in a representative high-performance plasma discharge projected for the new JT-60SA tokamak. The discharge features a double-null separatrix, 41 MW of combined neutral beam heating and electron cyclotron heating, and a high predicted ratio of the normalized plasma kinetic to magnetic pressure β . When considering input parameters computed from reduced transport models, gyrokinetic simulations predict a turbulent heat flux well below the injected 41 MW. Increasing the background gradients, on the other hand, can trigger a non-zonal transition (NZT), causing heat fluxes to no longer saturate. Furthermore, when considering fast ions in the simulations, a high-frequency mode is destabilized that substantially impacts the turbulence. The NZT is avoided by reducing the electron pressure by 10% below its nominal value, and the fast-ion resonance is removed by reducing the fast-ion temperature. The thus-obtained simulation features broadband frequency spectra and density and temperature fluctuation levels δ n / n ≈ 1 % –2%, δ T / T ≈ 1 % –6% that should be measurable with fluctuation diagnostics planned for JT-60SA. The temperature profile is fixed by the critical main-ion temperature gradient as a consequence of the high stiffness; heat fluxes increase by a factor of ten when increasing the main ion temperature gradient by 17%. Despite large gradients, it is demonstrated that, due to the large β , retaining compressional magnetic field fluctuations and in particular, the contribution of the pressure gradient in the ∇ B drifts, is crucial to achieving non-zero heat fluxes.
ISSN:0029-5515
1741-4326
DOI:10.1088/1741-4326/ad0c0a