天体高分辨率软X射线光谱的实验测量标定

Experimental Measurement and Calibration of Celestial Bodies with High Resolution Soft X-ray Radiation

近年来,利用实验装置测量的原子数据对一些天文观测难题(包括弱线辐射、诊断特征线比的标定和反常线流量比)的解释取得了很大的进展。为测量高电荷铁离子的高分辨率软X射线光谱,在国家天文台EBIS-A平台上设计并搭建了一个超高真空平场光谱仪。在单缝模式下,使用1200槽/毫米变间距的衍射光栅,测量波长为11.5~19.8 nm。针对光谱仪的测量结果,对可能测量的辐射进行理论预测。根据电子束离子阱的工作原理,基于Chianti数据库对海德堡电子束离子阱(Heidelberg-Electron Beam Ion Trap,EBIT)极紫外光谱数据(11.5~14.5 nm)进行分析。首先,建立线性回归模型校准由实验系统引起的线强度峰值位置的偏移;然后,通过碰撞辐射模型模拟的不同离化态铁离子的软X射线光谱确定实验测量中Fe VIII,Fe XIX-XXIII的线辐射,并较好地呈现观测谱。此外,在13.2925±0.10178 nm处发现了相对Fe XXIII跃迁线强度较弱的Fe XIX和Fe XX的混合线,而观测到的光谱没有分辨出这些弱线。因此,接下来的实验测量可以参考这一预测结果检验光谱仪的性能。

In recent years,using the atomic data measured by experimental devices to explain astronomical observational puzzles(including weak lines radiation,calibration of diagnostic characteristic lines ratio and anomalous lines flux ratio)has made great strides.In order to measure the high-resolution soft X-ray spectra of highly charged iron ions,an ultra-high vacuum flat field spectrometer is designed and built on the National Astronomical Observatories of the Chinese Academy of Sciences(NAOC)EBIS-A platform.In single-slit mode,the spectrometer uses 1200 grooves/mm varied line-spacing diffraction grating in the wavelength range of 11.5-19.8 nm.With the same working principle of the electron beam ion trap,Heidelberg-EBIT ultraviolet spectrometer experiment data based on Chianti database is analyzed in the spectral region from 11.5 to 14.5 nm.First,a linear regression model is established to calibrate the offset of the peak position of line strength caused by the experimental system.Then the soft X-ray spectra of Fe ions in various ionization stage simulated by the collision radiation model identifies wavelengths of Fe VIII and Fe XIX-XXIII line radiation in experimental measurement.And the present simulations satisfactorily reproduce the measured spectra.Furthermore,blend lines of Fe XIX and Fe XX,which is weaker than the transition line of Fe XXIII,are found at 13.2925±0.10178 nm but the observed spectra has not resolved these weak lines.Therefore,the following experimental measurement can take the predicted results as a reference to test the performance of the spectrometer.