A 4.8 m3 unsegmented liquid scintillation detector at the underground Laboratori Nazionali del Gran Sasso has shown the feasibility of multi-ton low-background detectors operating to energies as low as 250 keV. Detector construction and the handling of large volumes of liquid scintillator to minimize the background are described. The scintillator, 1.5 g PPO/L-pseudocumene, is held in a flexible nylon vessel shielded by 1000 t of purified water. The active detector volume is viewed by 100 photomultipliers, which measure time and charge for each event, from which energy, position and pulse shape are deduced. On-line purification of the scintillator by water extraction, vacuum distillation and nitrogen stripping removed radioactive impurities. Upper limits were established of < 10−7 Bq/kg-scintillator for events with energies 250 keV < E < 800 keV, and < 10−9 Bq/kg-scintillator due to the decay products of uranium and thorium. The isotopic abundance of 14C/12C in the scintillator was shown to be approximately 10−18 by extending the energy window of the detector to 25–250 keV. The 14C abundance and uranium and thorium levels in the CTF are compatible with the Borexino Solar Neutrino Experiment.

A large-scale low-background liquid scintillation detector : the counting test facility at Gran Sasso / G. Alimonti, C. Arpesella, G. Bacchiocchi, M. Balata, G. Bellini, J. Benziger, S. Bonetti, A. Brigatti, L. Cadonati, F. P. Calaprice, R. Cavaletti, G. Cecchet, M. Chen, N. Darnton, A. De Bari, M. Deutsch, F. Elisei, F. von Feilitzsch, C. Galbiati, A. Garagiola, F. Gatti, M. G. Giammarchi, D. Giugni, T. Goldbrunner, A. Golubchikov, A. Goretti, S. Grabar, T. Hagner, F. Hartmann, R. von Hentig, G. Heusser, A. Ianni, J. Jochum, M. Johnson, M. Laubenstein, F. Loeser, P. Lombardi, S. Magni, S. Malvezzi, I. Manno, G. Manuzio, F. Masetti, U. Mazzucato, E. Meroni, M. Neff, S. Nisi, A. Nostro, L. Oberauer, A. Perotti, A. Preda, P. Raghavan, R.S. Raghavan, G. Ranucci, E. Resconi, P. Ruscitti, R. Scardaoni, S. Schoenert, O. Smirnov, R. Tartaglia, G. Testera, P. Ullucci, R.B. Vogelaar, S. Vitale, O. Zaimidoroga. - In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH. SECTION A, ACCELERATORS, SPECTROMETERS, DETECTORS AND ASSOCIATED EQUIPMENT. - ISSN 0168-9002. - 406:3(1998 Apr), pp. 411-426.

A large-scale low-background liquid scintillation detector : the counting test facility at Gran Sasso

G. Bellini;S. Bonetti;E. Meroni;
1998-04

Abstract

A 4.8 m3 unsegmented liquid scintillation detector at the underground Laboratori Nazionali del Gran Sasso has shown the feasibility of multi-ton low-background detectors operating to energies as low as 250 keV. Detector construction and the handling of large volumes of liquid scintillator to minimize the background are described. The scintillator, 1.5 g PPO/L-pseudocumene, is held in a flexible nylon vessel shielded by 1000 t of purified water. The active detector volume is viewed by 100 photomultipliers, which measure time and charge for each event, from which energy, position and pulse shape are deduced. On-line purification of the scintillator by water extraction, vacuum distillation and nitrogen stripping removed radioactive impurities. Upper limits were established of < 10−7 Bq/kg-scintillator for events with energies 250 keV < E < 800 keV, and < 10−9 Bq/kg-scintillator due to the decay products of uranium and thorium. The isotopic abundance of 14C/12C in the scintillator was shown to be approximately 10−18 by extending the energy window of the detector to 25–250 keV. The 14C abundance and uranium and thorium levels in the CTF are compatible with the Borexino Solar Neutrino Experiment.
solar neutrinos ; liquid scintillator
Settore FIS/04 - Fisica Nucleare e Subnucleare
Settore FIS/01 - Fisica Sperimentale
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/41942
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