In this paper, we used radio frequency (RF) full wave simulation to explore the feasibility of generating a density beat oscillation formed by high harmonic fast waves (HHFWs) in the National Spherical Tokamak Experiment-Upgrade (NSTX-U) and of measuring it numerically with 2D beam emission spectroscopy (BES). This oscillation is of interest as it can be used to determine the injected RF fields. We began by computing HHFW fields in NSTX-U under a variety of experimental conditions and antenna configurations with Petra-M, a 3D RF wavefield solver. These fields were then used to evaluate the amplitude of δn_e,beat/n_e0 in the volume of measurement, which we predict to be between 5 × 10⁻¹⁰ and 10⁻⁹, although it is highly dependent on plasma parameters. Trends in magnetic field, core temperature, core density, and antenna phasing are presented, and the parameters most suitable to this measurement are identified. Finally, we developed a synthetic BES diagnostic to compare the experimental BES signal against.

中文翻译：

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利用束发射光谱直接探测NSTX-U热核等离子体中高次谐波快波的范围研究

在本文中，我们使用射频 (RF) 全波模拟来探索在国家球形托卡马克实验升级 (NSTX-U) 中生成由高次谐波快波 (HHFW) 形成的密度拍频振荡并对其进行测量的可行性使用二维光束发射光谱 (BES) 进行数值计算。这种振荡很有趣，因为它可以用来确定注入的射频场。我们首先使用 3D RF 波场求解器 Petra-M 在各种实验条件和天线配置下计算 NSTX-U 中的 HHFW 场。然后使用这些场来评估测量体积中δn _{e , beat} / n _{e 0}的幅度，我们预测其介于 5 × 10 ^-10和 10^-9，尽管它高度依赖于等离子体参数。介绍了磁场、核心温度、核心密度和天线相位的趋势，并确定了最适合该测量的参数。最后，我们开发了一种合成 BES 诊断来比较实验 BES 信号。