Experimental and analysis methods in radiochemical experiments

Radiochemical experiments made the history of neutrino physics by achieving the first observation of solar neutrinos (Cl experiment) and the first detection of the fundamental solar neutrinos component (Ga experiments). They measured along decades the integral charged current interaction rate in the exposed target. The basic operation principle is the chemical separation of the few atoms of the new chemical species produced by the neutrino interactions from the rest of the target, and their individual counting in a low-background counter. The smallness of the expected interaction rate (1 event per day in a ton target) poses severe experimental challenges on the chemical and on the counting procedures. The main aspects related to the analysis techniques employed in solar neutrino experiments are reviewed and described, with a special focus given to the event selection and the statistical data treatment.