9420867 Calaprice The development of a new detector for live-time measurements of low energy solar neutrinos is proposed. To achieve the required low background conditions, the detector must be located underground and be made of materials of natural radiopurity. It consists of a large ultra pure liquid scintillator operation in the Gran Sasso underground laboratory in Italy. The required purity levels are unprecedented and much of the effort of this proposal will be to develop special detector materials by powerful purification methods. This detector will be the first of its kind and will be the lowest background detector in the world. The scintillator detector proposed here, which has become known as the Borexino experiment, is designed to detect the 7Be neutrino in live mode. The expected count rate in the 100 ton fiducial volume is about 50 per day. The essential requirement of this experiment is a large unsegmented detector with uranium and thorium radiopurities of better than 0.5fg/g. A prototype detector with mass of a 4tons is currently under construction to test the purity of the scintillator an other technic aspects of the design, the initial research effort is to complete the development of the scintillator vessel and the scintillator purification system an to install these in the prototype detector. The second major effort will be to employ the test facility to study the effectiveness of purification processes. The researcher will then design the full scale Borexino experiment. ***
