Karlsruhe 2024 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 6: Methods in astroparticle physics 1

T 6.5: Vortrag

Montag, 4. März 2024, 17:00–17:15, Geb. 20.30: 2.067

Crystallized polyethylene naphthalate as wavelength shifting reflector for LEGEND-1000 — •Maximilian Goldrunner¹, Brennan Hackett², Andreas Leonhardt¹, and Stefan Schönert¹ for the LEGEND collaboration — ¹Technical University of Munich, TUM School of Natural Sciences, Garching, Germany — ²Max Planck Institute for Physics, Garching, Germany

The future LEGEND-1000 experiment will search for the neutrinoless double-beta decay of Ge-76. For background suppression, 1,000 kg of high-purity germanium detectors will be employed in a liquid argon (LAr) volume. Particles traversing the LAr induce scintillation light with a wavelength peaking at 128nm. The scintillation light is converted to visible wavelength by wavelength shifters. To improve the background suppression in LEGEND-1000, optically inactive surfaces are covered with wavelength-shifting reflectors (WLSR) that also reflect the scintillation light to the LAr instrumentation. Polyethylene naphthalate (PEN) is a wavelength-shifting polymer already used in the precursor experiment LEGEND-200. PEN thin films can be crystallized to act as a WLSR without a separate reflector. In this work, we studied the crystallization of amorphous PEN by heating, characterized for reflectivity and wavelength-shifting efficiency, to find the optimal configuration. We present the first measurement under the relevant LAr conditions, namely for excitation with LAr scintillation light and at LAr temperature. We compare it with amorphous PEN and the TPB-based WLSR of LEGEND-200. The DFG supports this research through the Excellence Cluster ORIGINS and the SFB1258.

Keywords: LEGEND; Polyethylene Naphthalate; Wavelength Shifting Reflector; VUV Optics; Crystalization