Aligning the Thomson scattering and charge exchange recombination diagnostics using neutral beam emission at DIII-D

This work addresses discrepancies in the alignment of the H-mode pedestal profiles of the electron and ion properties in the DIII-D tokamak as measured by Thomson Scattering (TS) and Charge Exchange Recombination Spectroscopy (CER) diagnostics. While the alignment of these profiles is key for accurate studies of tokamak physics and plasma confinement, misalignments can occur due to inaccuracies, such as in magnetic equilibrium reconstructions required to map measurements in different poloidal and toroidal locations. Both FIDASIM, an established simulation package, and a simplified collisional radiative model are used to simulate neutral beam state densities and neutral beam emission. Simulated neutral beam emissions are calculated based on shifted TS profiles and compared to beam emission measurements from the Main Ion CER system to determine the best shift for aligning TS with CER. This analysis is performed on various DIII-D discharges.

本研究针对DIII-D托卡马克中，由汤姆逊散射（Thomson Scattering，TS）与电荷交换复合光谱（Charge Exchange Recombination Spectroscopy，CER）诊断测得的电子与离子属性的H模边缘台基剖面对齐偏差问题展开探讨。尽管此类剖面的对齐是开展托卡马克物理与等离子体约束精准研究的关键前提，但诸如将不同极向与环向位置的测量结果进行空间映射所需的磁平衡重建存在误差等因素，均可能引发对齐偏差。本研究采用了成熟的模拟软件包FIDASIM与简化的碰撞辐射模型，对中性束态密度及中性束发射过程进行模拟。基于经偏移修正的TS剖面计算模拟中性束发射量，并将其与主离子CER系统测得的束发射数据进行比对，以此确定可实现TS与CER剖面对齐的最优偏移量。该分析已在多轮DIII-D等离子体放电实验中完成。