• • • Ge measurements for SuperNEMO Radiopurity requirements for SuperNEMO • • • Status of the Ge detectors in LSM, Canfranc and Bordeaux Tentative schedule for future Ge measurements Frédéric PERROT, CENBG, IDEA meeting, Paris, November 19th 2007

• • • From NEMO-3 to SuperNEMO T1/2(bb0n) > ln2  M  e  Tobs Nexclu N A  NEMO-3 SuperNEMO Choice of isotope 100Mo 150Nd or 82Se 7 kg 100-200 kg Isotope mass M Efficiency e(bb0n) 8 % ~ 30 % Nexclu = f(BKG) Internal contaminations 208Tl and 214Bi in the bb foil 208Tl < 20 mBq/kg 214Bi < 300 mBq/kg 208Tl < 2 mBq/kg (If 82Se: 214Bi < 10 mBq/kg) Energy resolution FWHM 8% @3MeV 4% @3MeV T1/2(bb0n) > 2. 1024 y <mn> < 0.3 – 1.3 eV T1/2(bb0n) > 1026 y <mn> < 50 meV SENSITIVITY

• • • Possible design of one module of SuperNEMO Planar and modular design: ~ 100 kg of enriched isotopes (20 modules  5 kg) 1 module: Source (40 mg/cm2) 4 x 2,7 m2 Tracking : drift chamber ~3000 cells in Geiger mode Calorimeter: scintillators + PM between 100 and 1000 PM depending on the scintillator geometry 4 m 1 m 5 m Top view

• • • Internal background Requirements of Se sources for SuperNEMO A(214Bi) < 10 µBq/kg A(208Tl) < 2 µBq/kg Way to achieve these requirements: Selection of natural Se, enrichment in 82Se and purification Radiopurity measurements of Se powder with Ge spectrometers to quantify the efficiency of the purification method at a level of 0,1 mBq/kg Production of Se source foils Final characterization of the radiopurity of the bb source foils with the BiPo detector for 100 kg of Se sources and 1-2 kg per sample, a set of 50-100 radiopurity measurements with Ge have to be performed (one month per sample)

Purified and nonpurified natural Selenium from ITEP 2007 • • • Sample of Se source Purified and nonpurified natural Selenium from ITEP 2007 mBq/kg Time (h) 40K 60Co 137Cs 238U 226Ra 228Ra 228Th Nonpur. Se 160 59±11 < 0.9 < 0.6 < 48 10±1 12±2 6.4±1.3 Purified Se 278 < 7.3 < 1.02 4.7±0.8 < 49 < 2 6.5±1.4 All measurement was done in Modane with a 400 cm3 detector Problem of contamination by 137Cs during the purification,

• • • External background and radiopurity of materials Natural radioactivity outside the foils may produce events only up to 2.2 MeV but: (a,n) reactions can produce events around 3 MeV radon emanation from materials may pollute the source foils in 214Bi and 210Pb need to measure 214Bi, 208Tl and also 238U (a emitter), 210Pb List of materials surrounding the source foils: Calorimeter (photomultiplier tubes, scintillators, mechanical support…) Tracking chamber (wires, mechanical support…) Shieldings Electronic component …

SuperNEMO requirements • • • Radiopurity measurements of PMT glass Collaboration CENBG, LSM, Photonis (Brive-la-Gaillarde) and PrimeVerre (Montpellier) Elaboration of a very low-background glass with a synthetic silica in progress Activity (Bq/kg) 40K 214Bi 208Tl NEMO3 PMT Hamamatsu 3.7±0.2 0.36±0.02 0.05±0.02 SuperNEMO requirements < 0.04 <0.005 <0.002 need to reduce the radiopurity by 2 orders of magnitude

Radiopurity requirements for SuperNEMO • • • Radiopurity of PMT glass 100 Standard glass Glass (=silica+…) 214Bi standard Schott PC screen Philips Chinese Plowden 10 Prime verre bottle quartz NEMO3 Burle Only silice 1 Activity Bq/kg bulb window 0,1 Glass of NEMO3 PMT (Hamamatsu) Radiopurity requirements for SuperNEMO 0,01 Samples Next step: measurements to select the best samples for the glass elaboration

• • • Radiopurity of other components in PMT In SuperNEMO, the other components must have a good radiopurity depending on their masses: Glass: ~500g/PMT if we choose 8’’, ~250 kg per module Magnetic shield (µ-metal): ~5 kg/PMT if 8’’, ~2500 kg per module! Ceramics: low mass but bad radioputity (to be improved) Insulators … R&D program has been started with Photonis and Primeverre in order to process a low backgorund PMT prototype end of 2008

Ge measurements at LSM (Modane) Ge measurements at Canfranc • • • Status of the Ge detectors available for SuperNEMO Ge measurements at LSM (Modane) Ge measurements at Canfranc Ge measurements at CENBG (Bordeaux)

Archeological lead (10 cm) • • • Low background Ge detectors at LSM 2 coaxial-type Ge detectors (400 cm3) dedicated to SuperNEMO radiopurity measurements for 214Bi and 208Tl 1 coaxial-type Ge detector (200 cm3) 1 new planar broad energy Ge detector (~200 cm3) for 238U and 210Pb Liquid nitrogen sample Standard lead (15 cm) Archeological lead (10 cm) Ge crystal 400 cm3 copper (10 cm) Counting rate of the 400 cm3 coaxial-type Ge detector around 0,2 count/min Sensitivity for 1 kg, 1 month: 214Bi ~200 µBq/kg 208Tl ~60 µBq/kg

• • • New shielding with neutron moderator at LSM

• • • Low background Ge detectors at Canfranc 2 coaxial-type Ge detectors (~400 cm3) dedicated to SuperNEMO radiopurity measurements have been receipt in 2007 in the old Canfranc laboratory up to now, due to the fact that the new Canfranc laboratory is temporarely closed, they are not installed in their shielding and can’t be used for radiopurity measurements we hope these detectors will be available in the second part of 2008

• • • Timelines for radiopurity measurements   4th term 2007 1st term 2008 2nd term 2008 3rd term 2008 4th term 2008 Measurements of radioactivity at Modane/Bordeaux Samples of Se BiPo materials PMT glass and others components… Detector for thoron measurements Development at Bordeaux (PhD Thesis started in Oct.2007) Measurements of radioactivity at Canfranc Restart of activities at Canfranc lab Installation of Ge detectors and shieldings, Commissioning Measurements Checking of previous background characterization of new Canfranc lab Gamma, muon and neutron flux measurements at new facilities

Scintillator (muon veto) • • • Low background Ge detectors at Bordeaux 1 coaxial-type Ge detector (100 cm3) for SuperNEMO and applications 1 well-type Ge detector (300 cm3) for 238U (63 keV) and 210Pb (46 keV) for SuperNEMO and applications Scintillator (muon veto) Archeological lead Ge crystal 100 cm3 Sample g boron polyethylene cryostat standard lead Sensitivity for 100 g, 1 week: ~10-50 mBq/kg, can only be used for rough measurements

Schedule 2007 2008 2009 2010 2011 2012 2013 NEMO3 Running R&D SuperNEMO BiPo Modane BiPo construction BiPo installation BiPo running @ Canfranc SuperNEMO 1st module construction Preparation of the site construction of 20 modules 6 SuperNEMO modules running @ Canfranc Final SuperNEMO modules installation RUNNING of Full detector

• • • Timelines for Ge measurements The number of samples to be measured for the SuperNEMO R&D and to construct the 1st module will increase in the next 2 years: samples of Se to be measured before and after purification radiopurity of the components of the PMT’s to reach a total radioactivity lower than 0.1 Bq/kg for one PMT (glass, µ-metal, ceramics…) (end of 2008) materials for the tracking chamber prototype (2008) materials for the BiPo detector (2008-2009) We will need an additional detector to enhance our measurements capability a 600 cm3 Ge detector with 5 kg of sample for 214Bi and 208Tl