High-resolution soft-X-ray beamline ADRESS at Swiss Light Source for resonant inelastic X-ray scattering and angle-resolved photoelectron spectroscopies

TL;DR

This paper details the design, technical realization, and capabilities of the high-resolution ADRESS soft-X-ray beamline at Swiss Light Source, optimized for RIXS and ARPES with high flux, resolution, and polarization control.

Contribution

It introduces a novel fixed-gap undulator design and optimized optics enabling high flux and resolution for soft-X-ray spectroscopy at the Swiss Light Source.

Findings

Achieves a resolving power above 33000 at 1 keV

Delivers photon flux up to 1.0e13 photons/sec/0.01%BW at 1 keV

Provides a vertical spot size of 4 micrometers for high-resolution spectroscopy

Abstract

We describe the concepts and technical realization of the high-resolution soft-X-ray beamline ADRESS operating in the energy range from 300 to 1600 eV and intended for Resonant Inelastic X-ray Scattering (RIXS) and Angle-Resolved Photoelectron Spectroscopy (ARPES). The photon source is an undulator of novel fixed-gap design where longitudinal movement of permanent magnetic arrays controls not only the light polarization (including circular and 0-180 deg rotatable linear polarizations) but also the energy without changing the gap. The beamline optics is based on the well-established scheme of plane grating monochromator (PGM) operating in collimated light. The ultimate resolving power E/dE is above 33000 at 1 keV photon energy. The choice of blazed vs lamellar gratings and optimization of their profile parameters is described. Due to glancing angles on the mirrors as well as optimized groove densities and profiles of the gratings, high photon flux is achieved up to 1.0e13 photons/s/0.01%BW at 1 keV. Ellipsoidal refocusing optics used for the RIXS endstation demagnifies the vertical spot size down to 4 um, which allows slitless operation and thus maximal transmission of the high-resolution RIXS spectrometer delivering E/dE better than 11000 at 1 keV photon energy. Apart from the beamline optics, we give an overview of the control system, describe diagnostics and software tools, and discuss strategies used for the optical alignment. An introduction to the concepts and instrumental realization of the ARPES and RIXS endstations is given.