Indium-Loaded Liquid Scintillator for Low-Energy Solar-Neutrino Spectroscopy

Liquid scintillators loaded with indium up to 200 g/l have been made to study the feasibility of detecting solar neutrinos by the ${}_{}{}^{115}{}_{}{}^{}\mathrm{In}$ inverse $\beta$ reaction scheme of Raghavan. To evaluate the background contribution due to the natural $\beta$ decay of ${}_{}{}^{115}{}_{}{}^{}\mathrm{In}$, we have measured its $\beta$ spectrum and find $T_{\frac{1}{2}}=4.41\mathrm{}\left(25\right)\mathrm{}\times {10}^{14}$ y and $E_{\mathrm{endpoint}}=482\mathrm{}\left(15\right)\mathrm{}$ keV. A direct counting indium detector of solar neutrinos appears feasible and possible configurations for such an experiment are briefly discussed.