Light Absorption Properties of the High Quality Linear Alkylbenzene for the JUNO Experiment

TL;DR

This study investigates the light absorption properties of high-quality linear alkylbenzene (LAB) used in the JUNO neutrino detector, focusing on impurities' effects to enhance optical transparency for improved neutrino detection.

Contribution

It provides a detailed analysis of organic impurities in LAB and their impact on light absorption, aiding in optimizing LAB preparation for JUNO.

Findings

Impurities significantly affect LAB transparency in 350-450 nm range.

Gas chromatography mass spectrometry identified impurity structures.

Theoretical PCM TDDFT analysis elucidated impurities' absorption properties.

Abstract

The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multi-purpose underground liquid scintillator detector designed to determine the neutrino mass hierarchy, and measure the neutrino oscillation parameters. The excellent energy resolution and the large fiducial volume anticipated for the JUNO detector offer exciting opportunities for addressing many important topics in neutrino and astro-particle physics. Linear alkylbenzene (LAB) will be used as the solvent for the liquid scintillation system in the central detector of JUNO. The light attenuation lengths of LAB should be comparable to the diameter of the JUNO detector, hence very good optical transparency is required. However, the presence of impurities in the LAB renders an intrinsic limit for the transparency. This work focuses on the study of the effects of organic impurities in the LAB, and their light absorption properties particularly in the wavelength region of 350 to 450 nm. we have prepared LAB samples and measured their light attenuation lengths. These samples were then analyzed by a gas chromatography mass spectrometry, and the structure formulas of organic impurities were ascertained. These impurities' light absorption properties in the wavelength region of 350 to 550 nm were theoretically investigated with PCM TDDFT. The overall optical transparency of the LAB samples was studied, which would further help us in promoting the LAB preparation technique for the mass production thereof, thus improving the transparency of the high quality LAB samples in the near future.