衍射光栅已被广泛应用于同步辐射光源软X射线与真空紫外光栅单色器中,光栅线密度偏差会直接影响单色器的性能。为了检测光栅线密度的偏差,本文在合肥先进光源预研过程中搭建了长程面形仪(LTP)系统。使用自准直仪对LTP检测光栅系统在26 μrad内的检测精度进行了标定。利用LTP对自主研制的760 line/mm与2400 line/mm等间距光栅进行线密度均匀性检测,使用干涉仪对760 line/mm光栅进行0级与1级衍射波前检测,并将检测结果与LTP测量结果进行比较。结果表明:系统标定的均方根误差为30 nrad,与干涉仪检测结果相比,两者同位置处的高度轮廓曲线具有较好的一致性。这说明搭建的LTP系统具有较高精度的检测光栅线密度的能力,为检测同步辐射光栅线密度的变化提供了平台。

Diffraction gratings are widely used in the soft X-ray and vacuum ultraviolet grating monochromators of the synchrotron radiation source, and thus the deviation of the groove density of the gratings directly affects the performance of the monochromators. In order to detect the deviation of the groove density, we built a long trace profiler (LTP) system in the pre-research process of Hefei Advanced Light Source (HALS). First, an autocollimator was used to calibrate the detection accuracy of the LTP system within 26 μrad. Then, the LTP was applied to detect the groove density uniformity of the self-developed 760 line/mm and 2400 line/mm uniform-line-spacing diffraction gratings adopted in the pre-research of HALS. Furthermore, an interferometer was employed to detect the zeroth and first-order diffraction wavefronts of the 760 line/mm grating. Finally, the above detection results were compared with the LTP-based measurement results. The results show that the root mean square error of the system calibration is 30 nrad, and the height profile curves at the same position are in good agreement in terms of LTP detection and interferometer measurement. This indicates that the LTP system can detect the groove density of diffraction gratings with high precision, providing a platform for detecting the deviation of the groove density of synchrotron radiation gratings.