量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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The fast ion transport plays a key role in the simulation for developing operational scenarios. But the transport of fast ions in the perturbed field is complex compared with that of thermal ions since the transport depends on energy and pitch angle as well as a spatial coordinate. The Monte-Carlo approach can handle the transport in the straight forward way, however the approach is computationally expensive and is not suitable for scenario simulators. We need a computationally low-cost method or a reduced transport model. The island width in the phase space can be a characteristic scale of the transport. Thus, a simple method to determine the island width is useful to construct a reduced model. In this paper, we present a method to estimate the drift-orbit island-width from the velocity perturbation. We have derived an analytic expression for the drift-orbit island-width on a resonant toroidal canonical angular momentum surface in the same way how we estimate the magnetic island width from the magnetic perturbation on a resonant magnetic poloidal flux surface. Thus, we can avoid the issue, in our previous work, on the difference between the magnetic perturbation and velocity perturbation. We can also eliminate the cost for the Poincaré-map calculation of the magnetic perturbation. The estimated drift orbit island widths were compared with those from Poincaré maps obtained from a drift-orbit-following calculation. The estimated island widths well correlate with those from Poincaré maps within the error of about 15%. The island overlaps are also explained by the estimated island position and its width. The estimation method can provide an indicator to evaluate an overlapping threshold for chaotic orbits in the same way with the magnetic perturbation.
会議概要（会議名, 開催地, 会期, 主催者等）
The 16th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems - Theory of Plasma Instabilities (EPPI2019)
Analytical estimation of drift-orbit island-width for passing ions in static magnetic perturbation
