$^6$Li-loaded liquid scintillators produced by direct dissolution of compounds in diisopropylnaphthalene (DIPN)

The paper describes preparation of $^6$Li-loaded liquid scintillators by methods involving direct dissolution of $^6$Li salts in the commercial diisopropylnaphthalene (DIPN) solvent, without the formation of water-in-oil emulsions. Methods include incorporation of $^6$Li that, unlike previously reported formulations, does not require additions of water or a strong acid such as hydrochloric acid (HCl). Results of the conducted experiments show that dissolution of aromatic and aliphatic $^6$Li salts in DIPN can be easily achieved at 0.1- 0.3% by weight of atomic $^6$Li, using small additions of waterless surfactants, or mild carboxylic acids. An alternative way suggests incorporation of $^6$Li as a part of a surfactant molecule that can be dissolved in DIPN without any solubilizing additions. Proposed methods enable preparation of efficient $^6$Li-loaded liquid scintillators that, at a large scale of 50 cm, exhibit good pulse shape discrimination (PSD) properties combined with up to 107% of light output and up to 115% of the attenuation length measured relative to standard undoped EJ-309 liquid scintillator.