Hard X-ray Photoelectron Spectroscopy Beamline P22
This new undulator beamline in the PETRA III Ada Yonath hall will be dedicated for hard X-ray Photoelectron Spectroscopy (HAXPES) applications. The HAXPES activities presently located at beamline P09 [1] will be relocated to P22 when it is commissioned.
P22 will comprise a unique selection of techniques using specialized instruments built and operated in collaboration with external user groups. These includes HAXPES with optional spin detection using a 2D spin filter, HAXPEEM, k-space microscopy and ambient pressure HAXPES.
The X-ray source is a 2m long spectroscopy undulator in a high-β section covering an energy range between 2.4 and 30 keV. The primary LN2-cooled double Si-crystal monochromator comprises remotely interchangeable pairs of Si(111) and (311) crystals. For higher energy resolution requirements, a double channel-cut (4-bounce) post-monochromator is available which in addition implements a stage with diamond phase plates providing variable circular beam polarisation for the study of magnetic materials. Beam focusing is realized by horizontally deflecting mirrors, combining a cylindrical - plane mirror pair for the vertical with a plane elliptical bendable mirror located close to the experiments for the horizontal. The minimum spot size at the first instrument position will be <10x10 µm2 providing about 2x1013 ph/s (Si(111) at 4-6 keV). Prior to the availability of the elliptical mirror, a 1D Be-lens transfocator will be used for horizontal focusing down to about 70x10 µm2 on the sample.
The experimental hutch is offering ample space for two in-line experimental end stations. Additional space - equipped with media - is available outside for off-line preparation and commissioning of further experimental set-ups.
The main instrument at P22 will be the established HAXPES setup relocated from beamline P09 which has been continuously upgraded and extended. It provides an optional wide-angle acceptance lens for increased transmission and/or angle resolved studies. In addition, an add-on detector employing an improved 2D spin filter detection scheme is currently being developed for this instrument in collaboration with user groups [2]. The second setup is a HAXPEEM instrument which has been developed and commissioned in the recent years [3] for spectro-microscopy applications utilizing the depth sensitivity in the keV energy range. In addition, a newly developed instrument for high-pressure HAXPES for energy and catalysis operando studies at real conditions up to 10 bar [4] will be used at P22.
As a further development, a novel instrument combining full-field k-microscopy with time-of-flight parallel energy recording will be tested at the beamline to measure the 4D spectral function ρ(EB;k) of suitable materials in the HAXPES regime. This setup makes use of the unique PETRA III timing mode and has successfully been used recently in the XUV regime [5].
Collaborating groups
Prof. Ralph Claessen et al., University of Würzburg
Prof. Gerd Schönhense et al., University of Mainz
Prof. Claus M. Schneider et al., Research Center Jülich
Prof. Anders Nilsson et al., Stockholm university
References
[1] A. Gloskovskii et al., J. Electron. Spectrosc. Relat. Phenom.185, 47 (2012).
[2] Collaboration with R. Claessen (Univ. Würzburg), G. Schönhense (Univ. Mainz).
[3] M. Patt et al., Rev. Sci. Inst. 85, 113704 (2014).
[4] Collaboration with A. Nielsson (Stockholm University).
[5] K. Medjanik et al., Nature Materials 16, 615 (2017).
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