CTF and low background facility at Gran Sasso A. Ianni a , M. Laubenstein a and Y. Suvorov a a INFN, Gran Sasso Laboratory, Assergi (AQ), Italy nting Test Facility of Borexino (CTF) is a 4-ton nted liquid scintillator detector located at the Gran nderground Laboratory. CTF is equipped with 100 d an active muon veto system. The CTF at present is with PC (C 9 H 12 ) inside a 500m thick nylon vessel. A second essel is present outside the scintillator vessel to decrease usion toward the core of the detector. ns of High Purity Water produced at the Gran Sasso ory shields the scintillator against neutrons from the ding rocks. Spectrum of prompt events in the scintillator of CTF Low background facility at the Gran Sasso Laboratory CTF:4-ton liquid scintillator side the CTF tank and above the water shielding. The nitrogen is continuously flushed in and realised, in order to have mbar. This n diffusion into the CTF tank. In the Hall C of the Gran Sasso Laboratory, where the CTF is located, the Rn in the air he nitrogen an electrostatic chamber(30kVolts) of 0.42m 3 has been installed on top of the water tank. A dedicated set-up , perform a deumidification and pushes the gas inside the chamber. Here an alpha detector is at work to measure the termine the activity. This set-up can reach a sensitivity of the order of 0.5mBq/m 3 . The Rn in the CTF blank is measured n in the air during important installation works and has been used during the inflation of the Borexino vessels. pectrum is a build-up effect after more than 3 years of operations. 204 days of livetime The screening of water, the active muon-veto and the Gran Sasso depth allow a zero-bacgkground spectrum above 3 MeV. The main source of background above 1 MeV is shown to be Rn from the shielding water. The activity of Rn in the shielding Water has been measured at the level of a few mBq/m 3 . Rn emanation and diffusion Through the nylon vessel is measured at the level of 10Bq/m 3 . Whole 4-ton mass Radial cut at 70cm for Reconstructed events Radial cut at 60cm for Reconstructed events 1 MeV n monitoring set-up for the CTF 210 Po 214 Po 218 Po Present Present : : on one floor in a service tunnel on one floor in a service tunnel Future Future : : in one dedicated three-storey in one dedicated three-storey building in hall A building in hall A nt the facility is equipped with 10 HpGe detectors (equipped with acrylic cover with continuous nitrogen flux for Rn shielding /kg), 1 Si-PIPS detector and 1 ultra low background liquid scintillator counter. The main purpose of the facility is mater experiments at Gran Sasso and background characterization. uture the new facility aims to: rbon and tritium measurements toring in air fic collaboration with experiments Ultra low liquid scintillator spectroscopy