@misc{oai:repo.qst.go.jp:00076760,
 author = {Shinohara, Kouji and Matsuyama, Akinobu and Bierwage, Andreas and Suzuki, Yasuhiro and Matsunaga, Go and Honda, Mitsuru and Sumida, Shuhei and Kim, Junghee and Shinohara, Koji and Matsuyama, Akinobu and Bierwage, Andreas and Matsunaga, Go and Honda, Mitsuru and Sumida, Shuhei},
 month = {Sep},
 note = {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., The 16th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems - Theory of Plasma Instabilities (EPPI2019)},
 title = {Analytical estimation of drift-orbit island-width for passing ions in static magnetic perturbation},
 year = {2019}
}