DAMA/NaI Experiment

Some of the main features of the set-up
  • Reduced standard contaminants (e.g. U/Th in the range of ppt) by material selection and growth/handling protocols;
  • PMTs: Each crystal coupled - through 10cm long tetrasil-B light guides acting as optical windows - to 2 low background EMI9265B53/FL (special development) 3 diameter PMTs working in coincidence;
  • Detectors inside a sealed Cu box maintained in HP Nitrogen atmosphere in slight overpressure;
  • Very low radioactive shields: 10 cm of Cu, 15 cm of Pb + shield from neutrons: Cd foils + polyethylene/paraffin+ ~ 1 m concrete moderator largely surrounding the set-up;
  • Installation sealed: a plexiglas box encloses the whole shield and is also maintained in HP Nitrogen atmosphere in slight overpressure. Walls, floor, etc. of inner installation sealed by Supronyl (2x10-11 cm2/s permeability).Three levels of sealing;
  • Installation in air conditioning + huge heat capacity of shield Calibration using the upper glove-box (equipped with compensation chamber) in HP Nitrogen atmosphere in slight overpressure calibration (in the same running conditions as the production runs);
  • Energy and threshold: Each PMT works at single photoelectron level. Energy threshold: 2 keV (from X-ray and Compton electron calibrations in the keV range and from the features of the noise rejection and efficiencies). Data collected from low energy up to MeV region, despite the hardware optimization was done for the low energy;
  • Pulse shape recorded over 3250 ns by Transient Digitizers;
  • Monitoring and alarm system continuously operating by self-controlled computer processes.