Numerical study of fast ion behavior in the presence of magnetic islands and toroidal field ripple in the EAST tokamak

• Published in: Chinese physics B Vol. 23; no. 10; pp. 334 - 341
• Main Author: 张伟 胡立群 孙有文 丁斯晔 张子君 刘松林
• Format: Journal Article
• Language: English
• Published: 01.10.2014
• Subjects: EAST; Magnetic islands; Magnetohydrodynamics; MHD; Orbits; Perturbation methods; Pitch angle; Ripples; Tokamak devices; Trapped particles; 快离子; 托卡马克; 数值研究; 波纹; 环向场; 磁岛; 行为
• ISSN: 1674-1056; 2058-3834; 1741-4199
• DOI: 10.1088/1674-1056/23/10/105201

A peculiar first orbit loss type was found apart from the normal ones when we use ORBIT code to simulate fast ion orbits in the EAST tokamak. Fast ion orbits were studied in the presence of toroidal field （TF） ripple and magnetohydro- dynamic （MHD） perturbations. We analyzed the properties of the drifted orbits in detail and compared their differences, finding that the combined effects of ripple and magnetic islands are much greater than the effects of either one of them alone. Then we investigated the orbitdeviations as a function of pitch angle in different radial positions. The modeling results demonstrate that the loss of trapped particles is mainly caused by the ripple, while MHD＇perturbation mainly plays an important role in the passing particles. Furthermore we modeled the loss rate using different equilibriums. Results prove that a higher beta can indeed improve the confinement of fast ions, while a little change in the q profile can make the topologies of magnetic islands become quite different and results in quite different total particle losses.