# Aging study of Gd concentration in LAB-based Gd loaded liquid scintillator exposed to passivated stainless steel

## TL;DR

This study investigates the long-term stability of Gd concentration in LAB-based Gd-loaded liquid scintillator stored in passivated stainless steel, finding minimal degradation over nearly two years, supporting stainless steel use in neutrino detectors.

## Contribution

It provides empirical evidence that passivated stainless steel does not significantly degrade Gd concentration in Gd-LS over extended storage periods.

## Key findings

- No significant change in neutron capture time after 602 days.
- Gd concentration remains stable within measurement uncertainty after 466 days.
- Estimated Gd degradation limit is 0.5% over 10 years.

## Abstract

Stainless steel is a candidate of the inner surface of the storage container for LAB-based Gadolinium loaded liquid scintillator (Gd-LS) to be used in the JSNS$^2$ neutrino detector. Aging effect on Gd concentration of Gd-LS was investigated with the Gd-LS sample stored in the passivated stainless steel bottle in two independent methods. The direct comparison of the neutron capture time measurement showed that there is no significant degradation of the capture time after 602 days aging. Titration was performed to measure Gd concentration, and the result after 466 days aging is consistent with the result before aging within the uncertainty of the measurement. The upper limit of degradation of Gd concentration in 21 kL tank case is estimated as 0.5 % for 10 years of storage. Both results lead to a conclusion that stainless steel is usable for Gd-LS storage for JSNS$^2$ experiment.