Ruben Reininger

A hybrid method for X-ray optics simulation: combining geometric ray-tracing and wavefront propagation

A new ’Hybrid Method’ combining ray-tracing and wavefront propagation for X-ray optics simulation is reported. The code is fast and can handle partially coherent sources, making it a useful tool for beamline design and optimization.

A soft x-ray beamline capable of canceling the performance impairment due to power absorbed on its optical elements

We present an entrance slitless beamline design capable of maintaining its very high performance in terms of energy resolution (>10(4)) and spot size (4x4 microm2) at the sample position despite being exposed to more than 2.15 kW of undulator radiation and a maximum power density on the optics of more than 0.9 W/mm2. Ray tracing simulations of this beamline under the worst-case thermal deformations of the optical element surfaces verify that appropriate focusing corrections are able to cancel the deleterious effects of these deformations. One of the necessary conditions for this cancellation is to illuminate the optical elements with a larger solid angle than the undulators central cone, which contains the usable photons but is considerably smaller than the angular power distribution.

Modular soft x-ray spectrometer for applications in energy sciences and quantum materials

Over the past decade, the advances in grating-based soft X-ray spectrometers have revolutionized the soft X-ray spectroscopies in materials research. However, these novel spectrometers are mostly dedicated designs, which cannot be easily adopted for applications with diverging demands. Here we present a versatile spectrometer design concept based on the Hettrick-Underwood optical scheme that uses modular mechanical components. The spectrometers optics chamber can be used with gratings operated in either inside or outside orders, and the detector assembly can be reconfigured accordingly. The spectrometer can be designed to have high spectral resolution, exceeding 10 000 resolving power when using small source (∼1μm) and detector pixels (∼5μm) with high line density gratings (∼3000 lines/mm), or high throughput at moderate resolution. We report two such spectrometers with slightly different design goals and optical parameters in this paper. We show that the spectrometer with high throughput and large energy window is particularly useful for studying the sustainable energy materials. We demonstrate that the extensive resonant inelastic X-ray scattering (RIXS) map of battery cathode material LiNi1/3Co1/3Mn1/3O2 can be produced in few hours using such a spectrometer. Unlike analyzing only a handful of RIXS spectra taken at selected excitation photon energies across the elemental absorption edges to determine various spectral features like the localized dd excitations and non-resonant fluorescence emissions, these features can be easily identified in the RIXS maps. Studying such RIXS maps could reveal novel transition metal redox in battery compounds that are sometimes hard to be unambiguously identified in X-ray absorption and emission spectra. We propose that this modular spectrometer design can serve as the platform for further customization to meet specific scientific demands.

DABAM: an open-source database of X-ray mirrors metrology

DABAM, an open-source database of X-ray mirrors metrology to be used with ray-tracing and wave-propagation codes for simulating the effect of the surface errors on the performance of a synchrotron radiation beamline.

A new compact soft x-ray spectrometer for resonant inelastic x-ray scattering studies at PETRA III

We present a newly designed compact grating spectrometer for the energy range from 210 eV to 1250 eV, which would include the Kα(1,2) emission lines of vital elements like C, N, and O. The spectrometer is based on a grazing incidence spherical varied line spacing grating with 2400 l/mm at its center and a radius of curvature of 58 542 mm. First, results show a resolving power of around 1000 at an energy of 550 eV and a working spectrometer for high vacuum (10(-4) mbar) environment without losing photon intensity.

Design of an ultrahigh-energy-resolution and wide-energy-range soft X-ray beamline

A new ultrahigh-energy-resolution and wide-energy-range soft X-ray beamline has been designed and is under construction at the Shanghai Synchrotron Radiation Facility. The beamline has two branches: one dedicated to angle-resolved photoemission spectroscopy (ARPES) and the other to photoelectron emission microscopy (PEEM). The two branches share the same plane-grating monochromator, which is equipped with four variable-line-spacing gratings and covers the 20-2000 eV energy range. Two elliptically polarized undulators are employed to provide photons with variable polarization, linear in every inclination and circular. The expected energy resolution is approximately 10 meV at 1000 eV with a flux of more than 3 × 10(10) photons s(-1) at the ARPES sample positions. The refocusing of both branches is based on Kirkpatrick-Baez pairs. The expected spot sizes when using a 10 µm exit slit are 15 µm × 5 µm (horizontal × vertical FWHM) at the ARPES station and 10 µm × 5 µm (horizontal × vertical FWHM) at the PEEM station. The use of plane optical elements upstream of the exit slit, a variable-line-spacing grating and a pre-mirror in the monochromator that allows the influence of the thermal deformation to be eliminated are essential for achieving the ultrahigh-energy resolution.

MERLIN — A meV Resolution Beamline at the ALS

An ultra‐high resolution beamline is being constructed at the Advanced Light Source (ALS) for the study of low energy excitations in strongly correlated systems with the use of high‐resolution inelastic scattering and angle‐resolved photoemission. This new beamline, given the acronym Merlin (for meV resolution line), will cover the energy range 10–150 eV. The monochromator has fixed entrance and exit slits and a plane mirror that can illuminate a spherical grating at the required angle of incidence (as in the SX‐700 mechanism). The monochromator can be operated in two different modes. In the highest resolution mode, the energy scanning requires translating the monochromator chamber (total travel 1.1 m) as well as rotating the grating and the plane mirror in front of the grating. The resolution in this mode is practically determined by the slits width. In the second mode, the scanning requires rotating the grating and the plane mirror. This mode can be used to scan a few eV without a significant resolution...

A new SHADOW update: integrating diffraction effects into ray-tracing

We describe the new implementation in the ray-tracing code SHADOW based on a “hybrid method” developed recently. The code calculates the diffraction effects from an optical element by means of wavefront propagation, and combines the result with that from regular ray-tracing. This hybrid procedure is invoked when diffraction is present (e.g., beam clipped by an aperture or the finite size of the optics) by user demand. The code enables the simulation of mirror figure errors in the framework of wave optics. The simulation of a complete beamline based on the far-field approximation is demonstrated. The near-field propagation is also implemented for individual optics. Finally, the applicable conditions and limitations of the new code are discussed.

Microfocusing at the PG1 beamline at FLASH

The Kirkpatrick–Baez (KB) refocusing mirrors unit at the PG1 beamline at FLASH has been newly designed, developed and fully commissioned. The vertical focal size of the KB optics is measured to be 5.8 ± 1 µm FWHM and the horizontal 6 ± 2 µm FWHM; astigmatism has been minimized to below 1 mm between waist positions. Such a tight focus is essential for the VUV double Raman spectrometer as it serves as an entrance slit for the first monochromator and defines its resolution to a very large extent. The Raman spectrometer is a permanent end-station at the PG1 beamline, dedicated to inelastic soft X-ray scattering experiments.

X-ray optics simulation and beamline design using a hybrid method: diffraction-limited focusing mirrors

A hybrid method combining ray-tracing and wavefront propagation was recently developed for X-ray optics simulation and beamline design optimization. One major application of the hybrid method is its ability to assess the effects of figure errors on the performance of focusing mirrors. In the present work, focusing profiles of mirrors with different figure errors are simulated using three available wave optics methods: the hybrid code based on the Fourier optics approach, the stationary phase approximation and a technique based on the direct Fresnel-Kirchhoff diffraction integral. The advantages and limitations of each wave optics method are discussed. We also present simulations performed using the figure errors of an elliptical cylinder mirror measured at APS using microstitching interferometry. These results show that the hybrid method provides accurate and quick evaluation of the expected mirror performance making it a useful tool for designing diffraction-limited focusing beamlines.