Evaluating Cryogenic Quantum Efficiency for DUNE's Calibration System Using the SLAC Cube LArTPC

The Deep Underground Neutrino Experiment (DUNE) aims to answer fundamental questions about neutrino mass ordering, CP violation, and the role of neutrinos in the early universe. Neutrinos are difficult to detect because they interact only via the weak force, producing rare signals that must be reconstructed with high precision. In DUNE's Liquid Argon Time Projection Chambers (LArTPCs), neutrinos interact with argon nuclei to produce charged particles, which ionize the argon as they travel. The resulting ionization electrons drift in an applied electric field and are read out to form the detector signal. To ensure this uniformity, DUNE employs a laser-based calibration system that uses the photoelectric effect to generate electrons at known locations inside the detector. This system depends on knowing the quantum efficiency (QE) of the photocathode material under cryogenic conditions, which determines how much charge is produced for a given amount of incident light. Because QE behavior at liquid-argon temperatures remains uncertain, we are evaluating it using a modular cube prototype at the Stanford Linear Accelerator (SLAC) designed to replicate DUNE's near detector optical environment. By studying photon-induced electron production under different configurations and cryogenic conditions, we aim to characterize QE behavior and its implications for the calibration system's accuracy. This presentation will discuss the calibration system and current status.