Photo-induced Charge Calibration in LXe for nEXO

The nEXO experiment is designed to search for the elusive neutrinoless double beta decay of $^{136}$Xe with a half-life sensitivity goal of $>10^{28}$ years using a $1.3$ m diameter cylindrical TPC with 5-tonnes of liquid xenon (LXe). The calibration of the ionization and scintillation light response of the detector involves the regular deployment of external radioactive sources which is challenging because of the excellent self-shielding properties of LXe, and the occasional injection of $^{220}$Rn and $^{127}$Xe. Several other risk-mitigating R\&D efforts are ongoing to incorporate additional calibration techniques to regularly monitor the drift electrons and the light response of silicon photomultipliers in liquid xenon. This talk presents the status, results and ongoing efforts at UMass, Amherst, deploying a dual grid ionization chamber with gold photocathode, to generate photoelectrons in LXe, measure QE and study long term stability of various components. We are also planning to test different photocathode materials. The use of multiple such photocathodes could allow monitoring the ionization electron lifetime almost continuously in nEXO.