Fu Shengyu, Yin Xianghui, Fu Jia, Li Yingying, Wang Fudi, Zhang Hongming, Bae Cheonho, Lyu Bo, Huang Qianhong, Shen Yongcai, Li Yichao, He Liang, Jin Yifei, Gong Xueyu
School of Nuclear Science and Technology, University of South China, Hengyang, Hunan 421001, China.
Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031, China.
Rev Sci Instrum. 2022 Apr 1;93(4):043504. doi: 10.1063/5.0083784.
Analyzing the radiation spectra of impurity ions is a widely applied diagnostic scheme for plasma ion temperature and rotation measurements on tokamaks. High precision wavelength calibration is a prerequisite for the accurate measurement of plasma parameters, especially for plasma rotation. Furthermore, the sparseness or absence of the standard spectral lines brings calibration challenges due to the narrow wavelength range. A precise wavelength calibration method is demonstrated in which the comb-like spectra generated by the Fabry-Pérot etalon can lock a series of fixed peaks as reference points in a wide wavelength range. The equal frequency intervals of the comb-like spectra are further corrected using several characteristic neon lines of known wavelengths. The experimental results indicate that the wavelength accuracy obtained by this calibration method is less than 0.005 nm, which corresponds to a rotation speed of 2.3 km/s in the toroidal direction for the beam emission spectroscopy spectrometer installed on the experimental advanced superconducting tokamak. Taking the O V(650.024 nm, n = 4 → 3) line as an example, the maximum difference in the oxygen ion rotation velocity is 3.8 km/s for the absolute rotation of ∼25 km/s, when compared with the calibration results of a standard lamp.
分析杂质离子的辐射光谱是托卡马克上用于等离子体离子温度和旋转测量的一种广泛应用的诊断方案。高精度波长校准是准确测量等离子体参数的前提条件，特别是对于等离子体旋转测量。此外，由于波长范围狭窄，标准光谱线的稀疏或缺失带来了校准挑战。本文展示了一种精确的波长校准方法，其中法布里 - 珀罗干涉仪产生的梳状光谱可以在宽波长范围内锁定一系列固定峰值作为参考点。利用几条已知波长的特征氖线对梳状光谱的等频率间隔进行进一步校正。实验结果表明，该校准方法获得的波长精度小于0.005 nm，对于安装在实验先进超导托卡马克上的束发射光谱仪，这对应于环向方向2.3 km/s的旋转速度。以O V(650.024 nm, n = 4 → 3)线为例，与标准灯的校准结果相比，对于约25 km/s的绝对旋转，氧离子旋转速度的最大差异为3.8 km/s。
