High-Resolution VUV-ARPES Beamline for Electronic Structure Studies at the Hefei Advanced Light Facility

Abstract A dedicated vacuum ultraviolet angle-resolved photoemission spectroscopy (VUV-ARPES) beamline is being constructed at the Hefei Advanced Light Facility (HALF) to support high-resolution electronic structure investigations of quantum materials. The beamline is designed to provide continuously tunable photons in the 6–135 eV energy range with full polarization control, combining high spectral resolution, high photon flux, and micron-scale focusing within a single experimental platform. The optical system is based on a 4.2 m elliptically polarizing undulator (EPU120), a high-resolution varied-line-spacing plane grating monochromator (VLS-PGM), and a Kirkpatrick–Baez refocusing system. The design target is a resolving power of 45,000 at 21 eV while maintaining photon flux suitable for demanding photoemission experiments. The final focusing optics are optimized for micro-ARPES applications and are capable of delivering a beam spot of only 3 μm at the sample position. The endstation integrates a high-resolution hemispherical electron analyzer, ultralow-temperature sample environments, advanced sample preparation facilities, oxide molecular beam epitaxy (OMBE) growth capabilities, and ultrahigh-vacuum transfer infrastructure. The combination of broad photon energy coverage, high spectral resolution, and microfocused beam delivery provides a versatile platform for investigations of superconductors, topological materials, strongly correlated electron systems, low-dimensional materials, and artificially engineered quantum heterostructures.