The water purification system for the low background counting test facility of the Borexino experiment at Gran Sasso

1996
4 pages
Published in:
  • Nucl.Instrum.Meth.A 370 (1996) 605-608
Experiments:

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Abstract: (Elsevier)
The Borexino experiment, for the study of solar neutrino physics, requires radiopurity at the level of 5 × 10 −16 g/g 238 U equivalent (or 6 × 10 −9 Bq/kg) on a detector mass of many tons of scintillator. Feasibility studies are performed in a counting test facility now operating at LNGS, which consists of 4 t of liquid scintillator viewed by 100 photomultipliers and shielded by 100 t of water. The accomplishment of this goal requires the shielding liquid, water, to be at the 10 −13 g/g contamination level (1.2 × 10 −6 Bq/kg) or better. This paper describes the water purification system; it consists of a combination of several purification processes to remove particulate, radioactive ions, dissolved gases and other impurities. Residual contaminations are measured by analytical or direct-counting techniques. For radon measurement, particularly challenging at this low activity levels, a low background counting method has been developed.
  • neutrino: solar
  • scintillation counter: liquid
  • water: admixture
  • Gran Sasso