A Submicron Soft X-ray Photoemission Beamline at Diffraction-Limited Synchrotron Light Source HEPS

Abstract A soft X-ray beamline dedicated to probing micro- and nano-scale interfacial electronic structures has been commissioned at the High Energy Photon Source (HEPS), China’s newest fourth-generation synchrotron radiation facility. Designated as the High-resolution Nanoscale Electronic Structure Beamline (High-NESS), this facility employs photoelectron spectroscopy as its primary technique, delivering a high-flux photon beam with tunable polarization over an energy range of 100–2000 eV. The beam spot size is continuously adjustable from the millimeter scale down to sub-micrometer dimensions to accommodate diverse experimental configurations. The endstation is equipped with in situ sample preparation and ultrahigh-vacuum transfer systems, alongside advanced sample modulation capabilities including cryogenic cooling, mechanical stress application, and electric field control. Scheduled to commence user operation in 2026, High-NESS is poised to provide substantial scientific support for research in condensed matter physics, materials science, information technology, and related interdisciplinary fields. This paper presents the design philosophy, key optical components, and preliminary performance characteristics of the High-NESS beamline.