磁约束等离子体中杂质(特别是高Z杂质)的存在将大大增强等离子体辐射功率损失, 破坏等离子体的约束性能。 杂质行为的定量研究首先要求对杂质测量的光谱诊断系统进行绝对强度标定, 获得灵敏度响应曲线。 介绍了EAST托卡马克上的快速极紫外光谱仪系统绝对强度的原位标定方法。 在波长范围20～150 内, 通过对比极紫外(EUV)波段连续轫致辐射强度的计算值和测量值得到光谱仪的绝对强度标定。 在此过程中, 首先由(523±1) nm范围内可见连续轫致辐射强度的绝对测量值计算出有效电荷数Zeff, 进而结合电子温度和密度分布计算EUV波段连续轫致辐射强度； EUV波段连续轫致辐射强度的测量值即为不同波长处探测器的连续本底计数扣除背景噪声计数值。 对于较长波段范围130～280 , 通过对比等离子体中类锂杂质离子(Fe23+, Cr21+, Ar15+)和类钠杂质离子(Mo31+, Fe15+)发出的共振谱线对(跃迁分别为1s22s 2S1/2—1s22p 2P1/2, 3/2及2p63s 2S1/2—2p63p 2P1/2, 3/2)强度比的理论和实验值进行相对强度标定。 其中共振谱线对强度比的理论值由辐射碰撞模型计算得到, 模型中处在各个能级的离子数主要由电子碰撞激发, 去激发以及辐射衰变三个过程决定。 两种方法相结合, 实现了光谱仪20～280 范围的绝对强度标定。 考虑轫致辐射、 电子温度及电子密度的测量误差, 绝对标定误差约为30%。 在绝对标定的基础上, 我们对杂质特征谱线强度进行绝对测量, 并将测量结果与杂质输运程序结合ADAS(Atomic Data and Analysis Structure)原子数据库计算得到的模拟值进行比较, 进而估算等离子体中的杂质浓度。

In the magnetic confinement device, the existence of impurity, especially the high-Z impurity, will cause the large enhancement of the radiation power loss and serious degradation of plasma performance. Quantitative study of impurity behavior requires the absolute intensity calibration of spectroscopy diagnostic system for impurity firstly. In this work, a precise in-situ absolute intensity calibration of a fast-response flat-field extreme ultraviolet (EUV) spectrometer is carried out by using different methods in different wavelength range. In the range of 20～150 , the sensitivity curve is obtained by comparing EUV bremsstrahlung between the measurement and calculation, in which the latter one is calculated by combining the profile of electron density, temperature and the effective charge Zeff deduced from the absolutely measured visible bremsstrahlung intensity in the range of (523±1) nm. The measured EUV bremsstrahlung intensity is the continuous counts subtracting the background noise at different wavelengths from the detector. In the longer wavelength range, i. e. 130～280 , the relative intensity calibration is addressed by comparing the measured and simulated line intensity ratio of resonance transition doubles from Li-like ions, e. g. Fe23+, Cr21+, Ar15+, and Na-like ions, e. g. Mo31+, Fe15+, with the transition of 1s22s2S1/2 —1s22p2P1/2, 3/2 and 2p63s2S1/2—2p63p2P1/2, 3/2, respectively. For the simulated line intensity ratio, it is modeled using the collisional-radiative model, in which the energy level populations are determined by electron collisional excitation, de-excitation and radiative decay. By combining those two methods, the absolute calibration of EUV spectrometer is achieved in the wavelength range of 20～280 . In addition, the uncertainty of the calibration is estimated to be about 30%, considering the measurement uncertainties of electron temperature, electron density and bremsstrahlung. Based on the obtained absolute sensitivity curve, the quantitative study of impurity concentration is being carried out by comparing the absolute measurement of emission line intensity with that simulated by combining the one-dimensional impurity transport simulation and ADAS (Atomic Data and Analysis Structure) database.