Status of the Borexino detector and the CTF results

Abstract The Borexino experiment, aimed at measuring the flux of 7 Be neutrinos from the Sun, is outlined and its importance is briefly discussed in the context of the present solar neutrino experimental scenario. The low energy of the 7 Be neutrinos presents new challenges in low background counting which have never before been reached; a 5-ton prototype Counting Test Facility has been running for about two years in the Gran Sasso Laboratory to demonstrate the feasibility of the experiment; some of the most relevant results are reported. The background requirements and design strategy of the full-scale detector are discussed with the expected final experimental performance.