Biednov Mykola, Brenner Günter, Dicke Benjamin, Weigelt Holger, Keitel Barbara, Rübhausen Michael, Dziarzhytski Siarhei
Institut für Nanostruktur- und Festkörperphysik, Universität Hamburg, Notkestrasse 85, Hamburg, 22607, Germany.
Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, Hamburg, 22607, Germany.
J Synchrotron Radiat. 2019 Jan 1;26(Pt 1):18-27. doi: 10.1107/S160057751801576X.
An extreme-ultraviolet (XUV) double-stage Raman spectrometer is permanently installed as an experimental end-station at the PG1 beamline of the soft X-ray/XUV free-electron laser in Hamburg, FLASH. The monochromator stages are designed according to the Czerny-Turner optical scheme, adapted for the XUV photon energy range, with optical elements installed at grazing-incidence angles. Such an optical scheme along with the usage of off-axis parabolic mirrors for light collimation and focusing allows for aberration-free spectral imaging on the optical axis. Combining the two monochromators in additive dispersion mode allows for reaching high resolution and superior stray light rejection, but puts high demands on the quality of the optical alignment. In order to align the instrument with the highest precision and to quantitatively characterize the instrument performance and thus the quality of the alignment, optical laser interferometry, Hartmann-Shack wavefront-sensing measurements as well as off-line soft X-ray measurements and extensive optical simulations were conducted. In this paper the concept of the alignment scheme and the procedure of the internal optical alignment are presented. Furthermore, results on the imaging quality and resolution of the first monochromator stage are shown.
一台极紫外（XUV）双级拉曼光谱仪被永久安装在汉堡FLASH软X射线/极紫外自由电子激光装置的PG1光束线的实验终端站。单色仪阶段是根据适用于极紫外光子能量范围的Czerny-Turner光学方案设计的，光学元件以掠入射角安装。这种光学方案以及使用离轴抛物面镜进行光准直和聚焦，使得在光轴上能够实现无像差光谱成像。以相加色散模式组合两个单色仪能够实现高分辨率和出色的杂散光抑制，但对光学对准质量提出了很高的要求。为了以最高精度对准仪器并定量表征仪器性能以及对准质量，进行了光学激光干涉测量、哈特曼-夏克波前传感测量以及离线软X射线测量和广泛的光学模拟。本文介绍了对准方案的概念和内部光学对准的过程。此外，还展示了第一单色仪阶段的成像质量和分辨率的结果。
