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Compact Fixed-exit UHV DCM for XAFS

2007; American Institute of Physics; Linguagem: Inglês

10.1063/1.2436208

1935-0465

Karen Rickers, U. Brüggmann, W. Drube, Mathias Herrmann, J. Heuer, Edmund Welter, H. Schulte‐Schrepping, H. Schulz-Ritter,

Particle Accelerators and Free-Electron Lasers

A double‐crystal, UHV‐compatible monochromator for XAFS applications at bending magnet beamlines has been designed. It uses two crystal sets, Si(111) and (311), on a common central rotation axis driven by an ex‐vacuo goniometer. All mechanical and electrical components are mounted on a 400 mm UHV flange which is attached to a compact vacuum chamber. The first crystals are water cooled using connector‐ and bellowless tubing through the fluidic sealed feedthrough of the central rotation. The first crystal set is mounted off‐axis and can be translated vertically to keep the fixed exit condition. The second crystal set uses small crystals of the same size as the first. In order to accept the reflected beam of the first crystal at small Bragg angles, it is tangentially translated along the beam. The angle can be varied from 5° to 55.5° resulting in a total energy range 2.4 – 43.4 keV for Si(111)/(311). Crystal sets are interchangeable by translating the vacuum chamber. Angle encoding is achieved by a Renishaw incremental optical encoder in vacuo.