Detection of low energy solar neutrinos by chambers of metastable superconducting granules

A brief reminder about solar neutrino detection is presented in order to stress the necessity of low-energy and real-time solar neutrino detection. It is shown, that two independent possible solutions exist for that purpose. Both of them are using as target and detectors large volumes of metastable superconducting granules. These solutions are: a) the inverse β decay reaction of neutrinos with indium. b) The detection of the recoil energy of a nuclei of the granule under the impact of a neutrino (coherent scattering discussed hereafter by Stodolsky). In the indium case, the energy threshold is 128 keV, in the coherent scattering it can, in principle, be lower than the 420 keV corresponding to the maximum energy of the neutrino produced by the proton-proton reaction. With the indium solution in mind the basic properties of metastable superconducting granules are presented together with a potential small scale detector