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Tracking (wire chamber)

Q b ( 214 Bi)=3.2 Me. Bi-Po Process. 238 U. 214 Po . ( 164 m s ). b. 214 Bi (19.9 mn). a. 210 Pb 22.3 y. Scintillator + PMT. 0.021%. 210 Tl (1.3 mn). Tracking (wire chamber). 232 Th. Source foil (40 mg/cm 2 ). 212 Po . ( 300 ns ). b. 212 Bi (60.5 mn). Shield

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Tracking (wire chamber)

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  1. Qb(214Bi)=3.2 Me Bi-Po Process 238U 214Po (164 ms) b 214Bi (19.9 mn) a 210Pb 22.3 y Scintillator + PMT 0.021% 210Tl (1.3 mn) Tracking (wire chamber) 232Th Source foil (40 mg/cm2) 212Po (300 ns) b 212Bi (60.5 mn) Shield radon, neutron,g a 208Pb (stable) 36% 2 modules 23 m2→ 12 m2 Background < 1 event / month e- a delay 208Tl (3.1 mn) R&D BiPo DETECTOR To measure the purity in 208Tl and 214Bi of the bb source foils before the installation in SuperNEMO Goal: To measure 5 kg of foils (12 m2, 40 mg/cm2) in 1 month with a sensitivity of: 208Tl < 2 mBq/kg and 214Bi < 10 mBq/kg

  2. e- prompt e- Bi-Po Process 238U 214Po Qb (212Bi) = 2.2 MeV a (164 ms) b 214Bi (19.9 mn) Delay a a 210Pb 22.3 y T1/2 ~ 300 ns Edeposited ~ 1 MeV Scintillator + PMT 0.021% 210Tl (1.3 mn) Tracking (wire chamber) 232Th Source foil (40 mg/cm2) 212Po (300 ns) b 212Bi (60.5 mn) Shield radon, neutron,g a 208Pb (stable) 36% 2 modules 23 m2→ 12 m2 Background < 1 event / month 208Tl (3.1 mn) R&D Detecteur BiPo To measure the purity in 208Tl and 214Bi of the bb source foils before the installation in SuperNEMO Goal: To measure 5 kg of foils (12 m2, 40 mg/cm2) in 1 month with a sensitivity of: 208Tl < 2 mBq/kg and 214Bi < 10 mBq/kg

  3. With 5 kg of 82Se source foil (~ 12 m2, 40 mg/cm2) 2 mBq/kg of 208Tl 50 (e-, delay a) 212Bi decays / month 3 events / month e ~ 6% Possible design Two modules, each module 2 x 3 m2 Calorimeter: 2 x 150 PMTs + Scint. Blocks 2 x 20 x 20 cm2 15 scint. Bars 2 m long, 2 x 20 cm2 Tracking: 4 layers of Geiger drift cells Magnetic field suitable to reject external e- Room needed: 4 x 5 m2 (with shield) + clean room beside the detector

  4. quenching a energy (MeV) Fit between 40 and 130 ns : T 1/2 = (212 +/- 65) ns ~ 300 ns expected Qb ~ 2.2 MeV Time delay between a and electron (in ns) electron energy (MeV) Analysis of such events in NEMO-3 data 1642 events obvserved in 1 year of data If all comes from mylar: 2.5 mBq/kg a 40 ns < Tdelay < 130 ns e- T0 electron (trigger)

  5. Origin of backgrounds surface contamination of 208Tl on the entrance surface of the lower scintillator Two prototypes to study the level of background

  6. Prototype BiPo-1 end 2005 – Jun. 2006 Air outlet + cables Surface of scintillators: Spottering of very thin layer of metal on the surface of the scintillators: 100 nm internal Al for reflecting + 100 nm external Au for cleaning PMT 5" NEMO3 Light guide « screan » to stop scintillation light Naked scintillator 20x 20 x 2cm We will use NEMO-3 equipments (5” PMTs, scintillator, etc…) 1 cm bored Polyethylen lead 10 cm bored Polyethylen Radon-tight enveloppe Radon-free air

  7. Prototype BiPo-2 Proto 2: Jun. 2006 – Jun. 2007 1 x 1 m2→ 25 x 2 PMTs (20 x 20 cm2)

  8. BiPo detector may become a new low background detector (like HPGe generation…) to measure 214Bi and 208Tl purity of thin materials (volume or surface) e- bb foils for SuperNEMO Capton foils for GERDA Cables ? etc… a Limitation of the thickness: 212Bi electron must cross the material • Final design must be studied depending on what we want to measure • The detector could be installed in Canfranc ?…

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