Measurement of the Quantum Efficiency of Electrode Materials for Vacuum Ultraviolet Photons in Liquid Xenon

Abstract Light dark matter searches using ionization signals in dual-phase liquid xenon (LXe) time projection chambers are limited by low-energy ionization backgrounds, including those from the photoelectric effect on the electrodes. To address this, we measured the quantum efficiency (QE) of various electrode materials for vacuum ultraviolet photons in LXe, including platinum (Pt), stainless steel (SUS304), and magnesium fluoride (MgF2)-coated aluminum (Al). Our results show that MgF2-coated Al exhibits the lowest QE among the tested materials. The QE for vacuum ultraviolet photons with a mean wavelength of 179.5 nm was measured to be (7.2 ± 2.3) × 10–5, corresponding to a reduction in QE by a factor of 4.4 compared to SUS304, a commonly used electrode material in direct dark matter experiments with LXe. These findings suggest that employing low-QE electrodes may help mitigate photoelectric-induced backgrounds, potentially improving the sensitivity of LXe time projection chambers in light dark matter searches.