The multiphase simulations are conducted with the kinetic-magnetohydrodynamics hybrid code MEGA to investigate the spatial and the velocity distributions of lost fast ions due to the Alfvén eigenmode (AE) bursts in the Large Helical Device plasmas. It is found that fast ions are lost along the divertor region with helical symmetry both before and during the AE burst except for the promptly lost particles. On the other hand, several peaks are present in the spatial distribution of lost fast ions along the divertor region. These peaks along the divertor region can be attributed to the deviation of the fast-ion orbits from the magnetic surfaces due to the grad-B and the curvature drifts. For comparison with the velocity distribution of lost fast ions measured by the fast-ion loss detector (FILD), the ‘numerical FILD’ which solves the Newton–Lorentz equation is constructed in the MEGA code. The velocity distribution of lost fast ions detected by the numerical FILD during AE burst is in good qualitative agreement with the experimental FILD measurements. During the AE burst, fast ions with high energy (100–180 keV) are detected by the numerical FILD, while co-going fast ions lost to the divertor region are the particles with energy lower than 50 keV.

中文翻译：

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大型螺旋装置中由 Alfvén 本征模式爆发引起的 NBI 快离子损失的混合模拟以及与快离子损失检测器测量的比较

使用动力学-磁流体动力学混合代码 MEGA 进行多相模拟，以研究由于大型螺旋器件等离子体中的 Alfvén 本征模式 (AE) 爆发而丢失的快离子的空间和速度分布。发现除了迅速丢失的粒子外，在 AE 爆发之前和期间，快离子沿着具有螺旋对称性的偏滤器区域丢失。另一方面，沿偏滤器区域丢失的快离子的空间分布中存在几个峰。沿偏滤器区域的这些峰可归因于由于梯度 B 和曲率漂移导致的快离子轨道与磁性表面的偏差。为了与快速离子损失检测器 (FILD) 测量的损失快离子的速度分布进行比较，求解牛顿-洛伦兹方程的“数值 FILD”是在 MEGA 代码中构建的。在 AE 爆发期间由数值 FILD 检测到的丢失快离子的速度分布与实验 FILD 测量结果具有很好的定性一致性。在 AE 爆发期间，数值 FILD 检测到具有高能量（100-180 keV）的快离子，而丢失到偏滤器区域的同向快离子是能量低于 50 keV 的粒子。