Ko Juyoung, Ko Jinseok
Korea Institute of Fusion Energy, Daejeon, South Korea.
Rev Sci Instrum. 2024 Aug 1;95(8). doi: 10.1063/5.0219593.
Measurement of the internal magnetic field is crucial for determining the equilibrium, stability, and current density of a plasma in a tokamak. A motional Stark Effect (MSE) diagnostic was developed to provide a measurement of the internal magnetic field in tokamaks by analyzing the emission from the interaction of the plasma particle with an injected neutral beam. The Stark effect causes the shifting and splitting of deuterium spectral lines due to the Lorentz electric field. However, it is difficult to accurately measure the internal magnetic field components since the radial electric field inherently formed inside the plasma is mixed with the Lorentz field. Under the circumstances in the Korea Superconducting Tokamak Advanced Research (KSTAR) device, one possible approach is to derive a radial electric field by measuring and comparing the polarization angles from the full and half-energy components of the neutral beam. To utilize the polychromatic MSE diagnostics in KSTAR, the half-energy component wavelength bands according to various magnetic field and beam energy combinations have been calculated, and the filter combinations required for those measurements have been selected. The Stokes-filter model used to evaluate the effect of multiple-ion-source neutral beam injection on the MSE measurements has been extended to infer the sensitivity of this approach to take the non-ideal bandpass filter effects into account.
测量内部磁场对于确定托卡马克中等离子体的平衡、稳定性和电流密度至关重要。一种运动斯塔克效应（MSE）诊断技术被开发出来，通过分析等离子体粒子与注入的中性束相互作用产生的辐射来测量托卡马克中的内部磁场。斯塔克效应会导致由于洛伦兹电场而使氘光谱线发生位移和分裂。然而，由于等离子体内部固有形成的径向电场与洛伦兹场混合在一起，因此难以准确测量内部磁场分量。在韩国超导托卡马克先进研究（KSTAR）装置的情况下，一种可能的方法是通过测量和比较中性束全能量和半能量分量的偏振角来推导径向电场。为了在KSTAR中利用多色MSE诊断技术，已经计算了根据各种磁场和束能量组合的半能量分量波长带，并选择了这些测量所需的滤波器组合。用于评估多离子源中性束注入对MSE测量影响的斯托克斯滤波器模型已得到扩展，以推断该方法考虑非理想带通滤波器效应时的灵敏度。
