Characterization of water-based liquid scintillator response to gammas and neutrons at varying scintillator-surfactant concentrations

Abstract

Large scale solar neutron and neutrino flux experiments require many tons of bulk liquid organic scintillator to take spectroscopic data of these energetic particles. However, material and chemical concerns make such experiments both challenging and costly. In their work, Winn and Raftery prepose a method of water-based scintillator as a viable alternative to liquid organic scintillator. Investigation into the light yield and light attenuation of this material is conducted, providing promising results. The scintillator pair PPO and POPOP serve as the primary and secondary fluor for the bulk scintillator, dissolved in Triton-X surfactant to fix the issue polar/non-polar solubility. A scintillator mixture comprised of 3.000 grams PPO, 0.075 grams POPOP, 240.0 grams of Triton-X diluted in deionized water is identified to produce optimal light yield. The relationship of response of the water-based liquid scintillator to Sodium-22 (²²Na) 511 keV gamma source and Americium-24 Beryllium (AmBe) 2-10 MeV neutron source is explored by taking pulse area spectra data at scintillator-surfactant concentrations of 0.5%, 1.0% and 2.0%. An analysis of light yield reveals an increasing linear correlation between observed count rates and increasing scintillator-surfactant concentration. Systematic error inherent in the experiment is discussed and suggestions for future work are proposed.