Optimum lithium loading of a liquid scintillator for neutron and neutrino detection

Neutral particle detection in high-background environments is greatly aided by the ability to easily load ⁶Li into liquid scintillators. We describe a readily available and inexpensive liquid scintillation cocktail stably loaded with a Li mass fraction up to 1 %. Compositions that give thermodynamically stable microemulsions (reverse-micellar systems) were explored, using a Compton spectrum quenching technique to distinguish these from unstable emulsions. Scintillation light yield and transmittance were characterized. Pulse shape discrimination (PSD) was measured using a ²⁵²Cf source, showing that electron-like and proton-like recoil events are well-resolved even for Li loading up to 1 %, providing a means of background suppression in neutron/neutrino detectors. While samples in this work were prepared with ^nat Li (7.59 % ⁶Li), the neutron capture peak was clearly visible in the PSD spectrum; this implies that while extremely high capture efficiency could be achieved with ⁶Li-enriched material, a very inexpensive neutron-sensitive detector can be prepared with ^nat Li.