An ultrahigh-vacuum multiple grating chamber and scan drive with improved grating change

Abstract

We describe a new grating chamber and scan drive which has been designed, built, and tested by the Physical Sciences Laboratory of the University of Wisconsin for the new high flux, high resolution spectroscopy branch line of the TOK hybrid wiggler/undulator on the NSLS VUV ring. The chamber will contain spherical gratings to be used in the Spherical Grating Monochromator (SGM) configuration introduced by Chen and Sette [1]. The grating chamber houses five 180 mm × 35 mm × 30 mm gratings capable of scanning a range of 12° (−4° to +8° with respect to the incoming beam direction) for VUV, and soft X-ray diffraction. The gratings can be switched and precisely indexed while under ultrahigh vacuum (UHV) at any scan angle and are mechanically isolated from the vacuum chamber to prevent inaccuracies due to chamber distortions. The gratings can separately be adjusted for height, yaw, patch, and roll, with the latter three performed in vacuo. The scan drive provides a resolution of 0.03 arc sec with linearity over the 12° range of ≅1.5 arc sec and absolute reproducibility of 1 arc sec.