The beamline is designed for specific techniques making use of photoelectron emission excited by X-rays in an energy range from 2.4 keV up to about 15 keV. Hard X-ray photoelectron spectroscopy (HAXPES) is developing at synchrotron laboratories worldwide because of its ability to probe the detailed electronic structure of solid materials with significantly higher depth sensitivity than conventional photoelectron spectroscopy. This makes it ideally suited for the investigation of bulk complex correlated materials, buried interfaces of multi-layered functional materials or as-grown samples without any need for prior in-situ surface treatment.
The X-ray source at P22 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 polarization for the study of magnetic materials. Beam focusing is realised 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 design minimum spot size at the first instrument position about 10x10 µm2 providing about 2x1013 ph/s (Si(111) at 4-6 keV). Additionally, a 1D Be-lens transfocator can be used optionally for horizontal focusing down to about 70x10 µm2 on the sample.
The beamline will comprise a unique selection of techniques using specialized instruments built and operated in collaboration with external user groups. The main instrument is the established HAXPES setup relocated from beamline P09. It provides an optional wide-angle lens for increased transmission and/or angle resolved studies. In addition, an add-on detector employing an improved 2D spin filter is currently being developed for this instrument in collaboration with user groups. The second setup is a HAXPEEM instrument which has been developed and commissioned in the recent years for spectro-microscopy applications utilizing the depth sensitivity in the keV energy range. In addition, a newly developed instrument for ambient pressure HAXPES for energy and catalysis in-operando studies at real conditions up to 10 bar will be operated at P22.