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Activity for the Gerda-specific part

Activity for the Gerda-specific part. Gerda geometry. top m -veto. water tank. neck. lead shielding. cryo vessel. Description of the Gerda setup including shielding (water tank, Cu tank, liquid Nitrogen), crystals array and kapton cables. Ge array. Small flux, small Ge volume:.

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Activity for the Gerda-specific part

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  1. Activity for the Gerda-specific part Gerda geometry top m-veto water tank neck lead shielding cryo vessel Description of the Gerda setup including shielding (water tank, Cu tank, liquid Nitrogen), crystals array and kapton cables Ge array

  2. Small flux, small Ge volume: 85 events/kg y Cosmic ray muons (Phase I) Flux at Gran Sasso: 1.1 m/m2 h (270 GeV) Further reduced by anti-coincidence with other Ge-crystals and with top (or Cerenkov) m-veto f from Lipari and Stanev, Phys. Rev. D 44 (1991) 3543 Input angular spectrum Input energy spectrum Teramo side Energy (keV) cosq

  3. Cosmic ray muons (Phase I) 9 Ge crystals for a total mass of 19 kg; threshold: 50 keV annihilation peak Sum spectrum without and with anticoincidence 5.5 years Energy (MeV) (1.5  2.5 MeV): 3.3·10-3 counts/keV kg y (~4·10-3 counts/keV kg y in H-M simul.) The anticoincidence between 9 crystals reduces the background index of a factor of 3 C. Doerr, NIM A 513 (2003) 596 1.5 MeV 2.5 MeV 1.0·10-3 cts/keV kg y Energy (MeV)

  4. Cosmic ray muons (Phase I) Small gain Position makes the difference Stable when changing the physics list No event with energy in crystal has less than that Top m-veto efficiency  sensitive to angular distribution Top m-veto below the penthouse is better. Cerenkov not strictly needed in Phase I ( very welcome!), necessary for Phase II

  5. Cerenkov muon veto Threshold 120 MeV  all events cut but two Energy (MeV) Energy deposit in the water (coincidence with detectors) 120 MeV in water (60 cm) correspond to 30,000 ph. Signal above 40-50 p.e. with 0.5% coverage  80-90 PMTs Optimization with MC light tracking has to be done

  6. Radon contamination in the water Simulated 800M 214Bi decays uniformly in the water tank 2 cts in 1 MeV Energy (MeV) Energy (MeV) Background index < 10-2 R [cts/kg keV y] (95% CL) 222Rn rate in Bq/m3 For 25 mBq/m3 < 2-3 · 10-4 cts/kg keV y (95% CL) For 5 mBq/m3 < 5 · 10-5 cts/kg keV y (95% CL)

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