The simultaneous measurement of energy and linear polarization of the scattered radiation in resonant inelastic soft x-ray scattering

Resonant Inelastic X-ray Scattering (RIXS) in the soft x-ray range is an element-specific energy-loss spectroscopy used to probe the electronic and magnetic excitations in strongly correlated solids. In the recent years, RIXS has been progressing very quickly in terms of energy resolution and understanding of the experimental results, but the interpretation of spectra could further improve, sometimes decisively, from a full knowledge of the polarization of incident and scattered photons. Here we present the first implementation, in a high resolution RIXS spectrometer used to analyze the scattered radiation, of a device allowing the measurement of the degree of linear polarization. The system, based on a graded W/B4C multilayer mirror installed in proximity of the CCD detector, has been installed on the AXES spectrometer at the ESRF; it has been fully characterized and it has been used for a demonstration experiment at the Cu L3 edge on a high-Tc superconducting cuprate. The loss in efficiency suffered by the spectrometer equipped with this test facility was a factor 17.5. We propose also a more advanced version, suitable for a routine use on the next generation of RIXS spectrometers and with an overall efficiency up to 10%.Comment: 26 pages, 8 figure

Depth-graded multilayers

We present first expérimental results on the fabrication and characterization of depthgraded x-ray multilayers providing a broad and well-defined reflectivity profile. We have designed and deposited irregular multilayer structures providing a practically constant reflectivity of about 20% around the first Bragg-reflection and a bandwidth of about 20% in both incident angle and photon energy. Detailed numerical simulations allow for the détermination of residual errors in the layer stack

Graded multilayers for fully polarization resolved Resonant Inelastic X-ray Scattering in the soft x-ray range

On the upgraded ESRF soft x-ray beamline ID32 a new spectrometer for Resonant X-ray Inelastic Scattering (RIXS) will be installed. To operate in fully polarized mode, a polarimeter will be inserted in the instrument to measure simultaneously the energy spectra and the linear polarization. The new spectrometer works between 500 eV and 1000 eV and requires graded multilayers to optimize the energy tunability and the polarization sensitivity. The present work covers the design, the fabrication, and the characterization of the multilayers. Performance evaluations during test and commissioning experiments with soft x-rays complement the paper