BOREXINO: the technical description

The BOREXINO apparatus is currently under construction in the Hall C of the LNGS underground labs. BOREXINO is a low-background detector to study the sub-MeV solar neutrino events (mainly ⁷Be) making use of a well-shielded ultrapure scintillator. The scintillation reaction that follows the scattering of the neutrinos on the electrons in the liquid is captured by 2200 phototubes which surround the 300 t of scintillator. The main difficulty of the experimental apparatus consists in the ultra-low radioactive background required for all the materials involved in the construction. Moreover, extremely strict cleanliness standards are mandatory for the operating conditions in order to avoid any further contamination coming from outside. The multi-shell structure of BOREXINO will avoid any contamination of the inner core of the liquid scintillator, perfectly suitable to carry out the challenging task of low-energy neutrino detection.