Measurement of impurity lines with two- crystal x-ray spectrometers on EAST

To simultaneously measure the He-like and H-like argon spectra, a two-crystal assembly has been deployed to replace the previous single crystal on the tangential x-ray crystal spectrometer. By selecting appropriate crystals with similar Bragg angles, plasma temperature in the range of 0.5 keV≦ T_e≦ 10 keV and rotation can be diagnosed based on the He-like and H-like argon spectra. However, due to the added complexity in the two-crystal assembly in which the spectra might be diffracted by two crystals, some additional impurity lines were identified. For example, tungsten (W) lines in different ionization states were diffracted by the He-like and H-like crystal. Additional molybdenum (Mo) lines in the wavelength range of He-like and H-like argon spectra lines were also summarized. The existence of these additional lines caused the fitted temperature to be different from the true values. This paper presents the identified lines through a comparison with available database, which should be included in the fitting procedure.     

EAST托卡马克上截面效应对电荷交换复合光谱测量结果的影响

离子温度和旋转速度是聚变等离子体中的重要物理参数,在先进实验超导托卡马克EAST(Experimental Advanced Superconducting Tokamak)上电荷交换复合光谱(Charge e Xchange Recombination Spectroscopy,CXRS)诊断是测量这些物理参数的标配诊断之一。由于截面效应的存在,CXRS诊断测量的谱线线型会受到影响,导致得到的离子温度和旋转速度偏离实际值,为了得到真实值,需要对离子温度和旋转速度进行修正。在EAST上,分别采用常用的动力学理论和数值计算方法对测量到的实验数据进行修正,同时对比两种方法对截面效应的修正结果,可以看出两种方法得到的结果趋势基本一致。对2015年EAST上电荷交换复合光谱测量到的典型的实验数据进行修正,结果表明在目前的放电条件下截面效应对离子温度的影响比较小,而对旋转速度的影响低于10%。