Karlsruhe 2024 – scientific programme

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T: Fachverband Teilchenphysik

T 13: Detectors 2 (scintillators, other)

T 13.1: Talk

Monday, March 4, 2024, 16:00–16:15, Geb. 30.23: 2/17

A novel cryogenic VUV spectrofluorometer for the characterization of wavelength shifters for the LEGEND-200 experiment — •Andreas Leonhardt¹, Maximilian Goldbrunner¹, Brennan Hackett², and Stefan Schönert¹ — ¹Technical University of Munich, TUM School of Natural Sciences, Garching, Germany — ²Max Planck Institute for Physics, Garching, Germany

We present a novel cryogenic VUV spectrofluorometer designed to characterize wavelength shifters (WLS) crucial for experiments based on liquid argon (LAr) scintillation light detection. Wavelength shifters like tetraphenyl butadiene (TPB) or polyethylene naphthalate (PEN) are used in these experiments to shift the VUV scintillation light to the visible region. Precise knowledge of the optical properties of the WLS at LAr temperature (87 K) and LAr scintillation wavelength (128 nm) is necessary to model and understand the detector response. The cryogenic VUV spectrofluorometer was commissioned to measure the emission spectra and relative wavelength shifting efficiency (WLSE) of samples between 300 K and 87 K for VUV (128 nm to 190 nm) and UV (310 nm) excitation. The TPB-based wavelength shifting reflector (WLSR) and amorphous PEN featured in the neutrinoless double-beta decay experiment LEGEND-200 were characterized as part of this work. A first measurement of their relative WLSE and emission spectrum at RT and 87 K is presented. Lastly, the response of the wavelength-shifting fibers used in LEGEND-200 to visible blue excitation is studied. This research is supported by the DFG through the Excellence Cluster ORIGINS and the SFB1258.

Keywords: LEGEND; Polyethylene Naphthalate; Tetraphenyl Butadiene; Wavelength Shifter; VUV Optics