Optimal Giant Detectors

Project Overview

The goal of our project was to generate an optimal formulation of Water-based Liquid Scintillator for antineutrino monitoring and radiation detection. The intent of these formulations was to support the Advanced Instrumentation Testbed by providing an alternative candidate media for large-underground antineutrino detectors. This work highlights the multidisciplinary nature of the Physical Life Sciences by utilizing the expertise of physicists in the Nuclear and Chemical Sciences Division and chemists within the Material Science Division.

In this study we formulated liquid scintillators that comprise a majority fraction of water and can discriminate between neutrons and gamma rays. By balancing the effects of interactions between the components of the formulation, these emulsions can be thermodynamically stable. This approach, which relates to a quantity known as the hydrophilic-lipophilic difference, requires consideration of the salinity and temperature as well as characterization of the surfactants and oil phase. We first characterized the relevant behavior of various oils in emulsions. Then, we introduced scintillating dyes and constructed partial phase diagrams of the emulsions.

From this study we developed water-based liquid scintillators (>50% water phase) that exhibited a light yield  as high as 18% of the light yield of a commercially available liquid scintillator that does not contain water and exhibited a figure of merit as high as 1.79 at 1500 keVee. The ability to distinguish nuclear and electronic recoils in large-underground detectors allows them to be more readily deployable through the reduction of muongenic fast-neutrons and accidentals.

Mission Impact

This project directly supports Lawrence Livermore National Laboratory's core competencies in Nuclear Threat Reduction by supporting advanced materials for far-field reactor monitoring and current NNSA funded activities in long-range neutrino monitoring. Further studies are underway to further characterize the performance of these materials and perform simulations to predict their impact on large-scale detectors. Additionally, the study of water-based liquid scintillators can influence long-baseline neutrino projects for the Office of Science, High Energy Physics.