A recently developed imaging neutral particle analyzer (INPA) on the DIII-D tokamak [X.D. Du et al., Nucl. Fusion 58, 082006 (2018)] enables fast ion velocity-space tomography of high fidelity at the interrogated phase space. To accomplish this, the spatial and energy depending fast (E < 80keV ) neutral flux towards the INPA stripping foils is calculated with FIDASIM and a newly developed code INPASIM simulates the INPA instrumental response to this neutral flux. Included in INPASIM is the neutral-foil interaction, the Larmor orbit tracing between the foil and the phosphor, the phosphor response to the incident ion flux as well as camera focusing. Benefiting from heavy, localized velocity-space weights and excellent signal to noise, computed tomography using the Ridge regression method is able to successfully reconstruct fine-scale velocity-space structures produced by multiple neutral beams separated by as small as ~ 3 keV in tests. Applying the inversion method to a sawtooth crash event reveals a significant profile flattening of confined passing particles across q = 1 flux surface, as well as a redistribution of fast ions into the trapped orbits at the plasma edge close to the last closed flux surface.

中文翻译：

---

解决成像中性粒子分析仪 (INPA) 测量中的快速离子分布

最近在 DIII-D 托卡马克上开发的成像中性粒子分析仪 (INPA) [XD Du 等人，Nucl. Fusion 58, 082006 (2018)] 能够在被询问的相空间中实现高保真度的快速离子速度空间断层扫描。为了实现这一点，使用 FIDASIM 计算了空间和能量依赖于 INPA 剥离箔的快速 (E < 80keV ) 中性通量，新开发的代码 INPASIM 模拟了 INPA 仪器对该中性通量的响应。INPASIM 包括中性箔相互作用、箔和磷光体之间的拉莫尔轨道追踪、磷光体对入射离子通量的响应以及相机聚焦。受益于沉重的局部速度空间权重和出色的信噪比，使用岭回归方法的计算机断层扫描能够成功地重建由多个中性光束产生的精细速度空间结构，这些中性光束在测试中间隔小至约 3 keV。将反演方法应用于锯齿形碰撞事件，揭示了穿过 q = 1 通量表面的受限通过粒子的显着轮廓变平，以及快速离子重新分布到靠近最后一个闭合通量表面的等离子体边缘处的俘获轨道中。