Münster 1999 – scientific programme

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O: Oberflächenphysik

O 36: Poster (II)

O 36.81: Poster

Thursday, March 25, 1999, 20:00–22:30, Zelt

Design of a PGM for the U49/2 Undulator at BESSY II — •D.R. Batchelor1, R. Follath2, and D. Schmeißer11Lehrstuhl Angewandte Physik, BTU Cottbus, Erich Weinert Str. 1, 03044 Cottbus — 2BESSY II, Rudower Chaussee 5, 12489 Berlin

This poster describes the beamline proposed for the BESSY II U49/2 Undulator by the Collaborating Research Group of BTU Cottbus,
HMI Berlin and the TU Darmstadt. The beamline is designed with both high resolution electron spectroscopy, valence band measurements and PEEM in mind and utilises the wide energy range of the U49 Undulator 40−1500eV.

The design chosen is based on a Petersen PGM [1] but with the grating illuminated with parallel light [2]. This modification allows variation of the monochromator higher order content or resolution, spot size without changing the focus. The performance of the beamline was investigated using various programs available at BESSY. The Undulator character- istics were evaluated using both SMUT and WAVE, and the optical performance of the monochromator was checked using REFLEC and RAY.

The calculations show a resolving power of 2×104 with a flux of the order 1013 photons s−1 over the energy range covered by the mono- chromator. The maximum nominal second order contributions are ≈ 2% at 300 eV for the first Undulator harmonic and ≈ 9% for the third harmonic at 500 eV, both of which can be reduced by increasing the grating incidence angle and, or decreasing the Undulator Pinhole size.

[1] H. Petersen,Opt. Commun. 40 (1982) 402

[2] M. R. Howells,Nucl. Inst. and Methods 177 (1980) 127,
R. Follath and F. Senf,Nucl. Inst. and Methods A390 (1997) 388

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