Performances and stability of a 2.4 ton Gd organic liquid scintillator target for ν̄e detection

Abstract

In this paper we report the performance and the chemical and physical properties of a 2 × 1.2 ton organic liquid scintillator target doped with Gd up to ∼ 0.1%, and the results of a 3 year long stability survey of the target. In particular we have measured and monitored the optical and fluorescent properties of the Gd-doped liquid scintillator (LS), the amount of both Gd and primary fluor in solution, and the performance of the two Gd doped targets as neutron detectors, namely neutron capture efficiency and average capture time. The experimental survey is ongoing, the targets being continuously monitored. From the spectrophotometric measurements performed on samples periodically extracted along the three years, we can exclude, at 99% C.L. level, a degradation of the light transmittance of the Gd-doped liquid scintillator larger than 1% y-1; from the in-tank measurements no significant decrease of the neutron capture efficiency and neutron capture time is observed. This is the largest stable Gd-doped organic liquid scintillator target ever produced and continuously operated for a long period.