In-Situ Measurement of Relative Attenuation Length of Gadolinium-Loaded Liquid Scintillator Using Source Data at RENO Experiment

We present an in-situ method of measuring the relative attenuation length of gadolinium-loaded liquid scintillator in the RENO detectors using radioactive source calibration data without requiring any PMT performance model. We observed the degradation of the attenuation length of the gadolinium-loaded liquid scintillator in the RENO detectors by ~50% over a period of about 4 years.