Heilmann Ralf K, Kolodziejczak Jeffery, Bruccoleri Alexander R, Gaskin Jessica A, Schattenburg Mark L
Appl Opt. 2019 Feb 10;58(5):1223-1238. doi: 10.1364/AO.58.001223.
We present measurements of the resolving power of a soft x-ray spectrometer consisting of 200 nm period lightweight, alignment-insensitive critical-angle transmission (CAT) gratings and a lightweight slumped-glass Wolter-I focusing mirror pair. We measure and model contributions from source, mirrors, detector pixel size, and grating period variation to the natural linewidth spectrum of the Al- doublet. Measuring up to the 18th diffraction order, we consistently obtain small broadening due to gratings corresponding to a minimum effective grating resolving power >10,000 with 90% confidence. Upper limits are often compatible with =∞. Independent fitting of different diffraction orders, as well as ensemble fitting of multiple orders at multiple wavelengths, gives compatible results. Our data leads to uncertainties for the Al- doublet linewidth and line separation parameters two to three times smaller than values found in the literature. Data from three different gratings are mutually compatible. This demonstrates that CAT gratings perform in excess of the requirements for the Arcus Explorer mission and are suitable for next-generation space-based x-ray spectrometer designs with resolving power five to 10 times higher than the transmission grating spectrometer onboard the Chandra X-ray Observatory.
我们展示了一种软X射线光谱仪分辨能力的测量结果，该光谱仪由周期为200 nm的轻质、对对准不敏感的临界角透射（CAT）光栅以及一对轻质 slumped玻璃沃尔特-Ⅰ型聚焦镜组成。我们测量并模拟了光源、镜子、探测器像素尺寸和光栅周期变化对Al- 双线自然线宽光谱的贡献。测量高达第18衍射级时，我们始终获得由于光栅导致的小展宽，对应于最小有效光栅分辨能力>10,000，置信度为90%。上限通常与 =∞兼容。对不同衍射级进行独立拟合，以及对多个波长的多个级进行整体拟合，都得到了兼容的结果。我们的数据导致Al- 双线线宽和线间距参数的不确定性比文献中发现的值小两到三倍。来自三个不同光栅的数据相互兼容。这表明CAT光栅的性能超过了Arcus Explorer任务的要求，适用于下一代天基X射线光谱仪设计，其分辨能力比钱德拉X射线天文台搭载的透射光栅光谱仪高五到十倍。
