IVC17 / ICSS13 and ICN+T 2007

The adress project at the swiss light source: a beamline for soft X-ray RIXS and arpes studies on correlated and nano-structured materials
Schmitt, Thorsten¹; Strocov, Vladimir¹; Schmidt, Thomas¹; Flechsig, Uwe¹; Chen, Qianhong¹; Krempaski, Juraj¹; Betemps, Robin¹; Kropf, Markus¹; Hess, Christoph¹; Widmer, Reto¹; Jaggi, Andreas¹; Raabe, Jörg¹; Imhof, Arthur¹; Jakob, Bruno¹; Vollenweider, Christian¹; Schönherr, Veit¹; Dubi, Fritz¹; Ghiringhelli, Giacomo²; Dallera, Claudia²; Piazzalunga, Andrea²; Braicovich, Lucio²; Wang, Xiaoqiang¹; Grioni, Marco¹; Patthey, Luc¹ ¹Switzerland; ²Italy

Resonant inelastic X-ray scattering (RIXS) is a powerful bulk-sensitive probe of the electronic structure of condensed matter with atomic and orbital sensitivity. It is a unique tool for determining the energy and symmetry of charge neutral electronic excitations in strongly correlated materials. Large probing depths of soft X-rays give access to buried nanostructure systems with RIXS. Angle-Resolved Photoelectron Spectroscopy (ARPES) allows k-resolved investigations of the electronic structure, correlation and resonance effects. Promoting ARPES into the soft X-ray range offers enhanced bulk sensitivity and better control over 3-dimensional k. Instrumentation for both, soft X-ray RIXS and ARPES, will soon become available for users at the ADvanced RESonant Spectroscopies (ADRESS) beamline at the Swiss Light Source (SLS) beginning with the RIXS end-station in the second half of 2007.
We report on construction and planned capabilities of the ADRESS beamline at the SLS. Its optical scheme is based on a Plane Grating Monochromator operated in collimated light. The beamline will deliver soft X-rays with variable polarization (circular and linear) between 0.4 and 1.8 keV at high resolving power up to 28000 near 1 keV. The expected flux of 1 keV photons on the sample ranges from 3x10¹¹ to 1x10¹³ photons/s/0.01%BW for a resolving power of 28000 and 7000, respectively. The undulator for this beamline adopts an Apple-type scheme with 4 arrays of permanent magnets with a fixed magnetic gap. In this design horizontal movements of the magnetic arrays are used to adjust polarization (opposite arrays) and photon energy (two adjacent arrays).
The RIXS end-station is equipped with a soft X-ray spectrometer (resolving power ~ 12000 for 1 keV) called SAXES (Super Advanced X-ray Emission Spectrograph) based on a variable line spacing spherical grating. This instrument promotes RIXS towards an ultra-high resolution technique. SAXES is installed on a rotating platform in order to study low-energy excitations as a function of momentum transfer. Ellipsoidal refocusing optics reduces the vertical beam dimension on the sample to below 10 µm as required for high detection efficiency of the inelastically scattered X-rays.

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