Extraction method for preparing indium-containing liquid organic scintillators for solar neutrino detection for LENS experiment, low-energy neutrino spectroscopy

Extraction of In with solutions of 2-methylvaleric acid (H2MVA) in trimethylbenzene (TMB) was studied. Depending on pH of the equilibrium aqueous phase, the extracted indium species are In(2MVA)3 · 3(H2MVA), In(2MVA)3, [In(2MVA)x(OH)3−x]n, etc., where 2MVA is the 2-methylvalerate anion and n is the degree of polymerization. By the extraction method, In-containing liquid organic scintillators (LOSs) with the following parameters were obtained: [In] = 50–96 g l−1, transparency 2–3 m, light output 68% relative to TMB. Long-term precision trials of the scintillators in the Gran Sasso underground laboratory (Italy) confirmed that the scintillator parameters were stable and met the requirements of the LENS experiment. A procedure was developed for preparing solid anhydrous indium hydroxycarboxylates, and their properties were studied. LOSs based on solutions of solid indium hydroxycarboxylates in TMB were prepared and subjected to long-term trials in which the transparency and light output were monitored. One of the major factors responsible for the instability of indium-containing LOSs is the presence of water in the organic phase.