Low-Energy Calibrations of LArTPCs with Ambient Radiogenic Sources and ²²⁰Rn Injection

The Deep Underground Neutrino Experiment (DUNE) aims to make precise measurements of neutrino oscillations. The experiment will consist of an intense neutrino beam produced at Fermilab near Chicago, Illinois, a Near Detector complex close to the neutrino beam production to measure neutrinos before oscillations, and a Far Detector located 800 miles away and about 1 mile underground to measure neutrinos after oscillations. For DUNE to accomplish its goals, it must achieve accurate spatial and calorimetric reconstruction of charged particles using Liquid Argon Time Projection Chambers (LArTPCs). This requires performing precise detector calibrations, which often includes the use of cosmic ray muons. They are abundant for detectors near the surface and have a well-known energy spectrum and loss, making them valuable for detector calibration. However, there are limited statistics of cosmic ray muons at the Far Detector, and the Near Detector which is 200 ft underground, presenting a need for more calibration techniques to calibrate them effectively. This presentation will describe results of low-energy radiological calibrations in the 2x2 Demonstrator, a prototype of the LArTPC component of the Near Detector complex. Results from a small-scale LArTPC at Colorado State University, the Colorado Argon Test Stand (CATS), will also be presented, including tests of ²²⁰Rn injection into liquid argon to support LArTPC calibration efforts.