Wonseok Bae Final Defense
Event starts on this day
Mar
26
2026
Featured Speaker(s):
Wonseok Bae
Event starts on this day
Mar
26
2026
Title: Advancing the Liquid-Argon Active Veto for the LEGEND Experiment
Description
Abstract: The LEGEND-1000 experiment is designed to search for neutrinoless double beta decay with unprecedented discovery potential, targeting half-lives beyond 10^28 years. Achieving this goal requires ultra-low background levels, where the liquid argon (LAr) active veto plays a crucial role. While optical fibers are essential for collecting LAr scintillation light, they also introduce intrinsic backgrounds from trace U-238 and Th-232 decay chains within the fibers.
This talk presents a novel background suppression strategy using newly developed scintillating-wavelength-shifting (Sci-WLS) fibers. Unlike standard WLS fibers, Sci-WLS fibers provide a self-veto capability by generating scintillation light from radioactive decays within the fibers. The optical performance and the response to the ionizing radiation of these fiber candidates—including emission spectra, attenuation lengths, and light yields—are systematically characterized using LED excitation and calibrated alpha, beta, and gamma sources. Furthermore, Geant4 Monte Carlo simulations quantify the suppression of Bi-214 and Tl-208 backgrounds. These results demonstrate that Sci-WLS fibers are a promising technology to meet the stringent background requirements and discovery sensitivity goals of LEGEND-1000.