Design and Construction of a High-Flux Vacuum Ultraviolet Photoionization Mass Spectrometry Beamline at the Hefei Advanced Light Facility

Abstract

The BL01 beamline at the Hefei Advanced Light Facility (HALF) is a dedicated vacuum ultraviolet (VUV) photoionization mass spectrometry beamline designed for energy conversion and astrochemistry research. Operating in the 5–20 eV photon energy range, BL01 employs a 4.2-m hybrid undulator (HU115) as its light source on a 2.2 GeV fourth-generation storage ring with an emittance below 100 pm·rad. The beamline features a dual-branch configuration (white-light and monochromatic branches) using a Monk–Gillieson monochromator with two variable-line-spacing plane gratings (150 and 300 lines/mm). The white-light branch is designed to deliver a photon flux of 1.0 × 1016 phs/s at 4% bandwidth and 10 eV, while the monochromatic branch is designed to achieve an energy resolution of 5000 at 15 eV with a photon flux of 2.0 × 1013 phs/s at a resolving power of 2000. Three dedicated endstations─combustion chemistry, catalysis chemistry, and astrochemistry─are equipped with high-resolution time-of-flight mass spectrometers (mass resolution ≥5000, detection limit 0.1 ppm), enabling in-situ detection of trace reaction intermediates across wide temperature (5–2000 K) and pressure (10–8 Pa to 20 bar) ranges. The high flux is expected to provide competitive advantages over existing international VUV photoionization beamlines, with a three- to ten-fold improvement in photon flux. The beamline is currently under construction, with completion expected in 2028.