1. • • • 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

2. • • • 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 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
T1/2(bb0n) > y
<mn> < 0.3 – 1.3 eV
T1/2(bb0n) > 1026 y
<mn> < 50 meV
SENSITIVITY

3. • • • 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

4. • • • 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 radiopurity measurements with Ge have to be performed (one month per sample)

5. 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,

6. • • • 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 …

7. 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

8. 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

9. • • • 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

10. 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)

11. 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

12. • • • New shielding with neutron moderator at LSM

13. • • • 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

14. • • • 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

15. 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

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

17. • • • 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 ( )
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