Conference Paper First-Principle Simulations Reproduce Multiple Cycles of Abrupt Large Relaxation Events in Beam-Driven JT-60U Plasmas

ビアワーゲ, アンドレアス  ,  篠原, 孝司  ,  藤堂, 泰  ,  相羽, 信行  ,  石川, 正男  ,  松永, 剛  ,  武智, 学  ,  藤間, 光徳  ,  矢木, 雅敏

Using the high-performance supercomputer Helios and advanced numerical methods, first-principle multi-time-scale simulations of fast-ion-driven magnetohydrodynamic modes have, for the first time, reproduced multiple cycles of so-called “Abrupt Large Events (ALE)” as observed in beam-driven high-beta JT-60U tokamak experiments. This is a major milestone because, unlike experiments, such simulations can provide us with physical information at arbitrary levels of detail. Moreover, these simulations yield more accurate and detailed predictions for the fast ion density profile and velocity distribution, even in the presence of intermittent strong shear Alfven mode activity such as ALEs. In this paper, we describe the numerical methods used, validate the results against experimental data from JT-60U, and present first new physics insights that were obtained from the analysis of the simulation results. For instance, it is found that ALEs occur when multiple fast-ion-driven modes with different toroidal wavelengths grow to large amplitudes while interacting nonlinearly. This multi-wavelength-nature of ALEs was subsequently confirmed experimentally.

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