Progress Toward Measuring the Ionization Yield of Germanium Using a SuperCDMS-Style High-Voltage (HV) Detector at NEXUS

The Super Cryogenic Dark Matter Search (SuperCDMS) SNOLAB experiment is currently under construction 2 km underground at the SNOLAB facility near Sudbury, Canada. The experiment will deploy 24 cryogenic germanium (Ge) and silicon (Si) calorimeter detectors, aiming to achieve world-leading sensitivity in the direct detection of dark matter particles interacting with nuclei, with a focus on masses between 0.5 and 5 GeV/c². One of the key challenges for the experiment is the uncertainty in the detector response to low-energy nuclear recoils (NRs). This response uncertainty introduces systematic effects that can limit the overall sensitivity of SuperCDMS. To address this, we plan to deploy a SuperCDMS-style Germanium HV detector at NEXUS, the Northwestern Experimental Underground Site, located in the MINOS cavern at Fermilab, to directly measure ionization yield and the detector response to sub-keV NRs in Ge. This measurement will serve as a critical input to detector response modeling and background discrimination. Progress on this calibration effort and related detector developments will be presented in this talk.