1. The CUORE experiment
Marisa Pedretti
INFN
Milano Bicocca

2. Outlook of the talk
- Sensitivity targets and experimental requirements for competitive 0νDBD experiments
- The 130Te characteristics
- The bolometric technique
From Cuoricino to CUORE experiment
CUORE experiment and its critical point
Conclusion

3. Target sensitivity
3 different value of neutrino mass can be seen as future milestones:
S. Pascoli, S. T. Petcov and T. Schwetz, hep-ph/
500 meV
50 meV
15 meV

4. Target sensitivity
In order to give an idea of the amazing challenge of the future sensitivity target I quoted the number of events expected in an year for 1 ton experiment assuming the correctness of the three neutrino mass milestones:
Counts / y ton Ge
natural
enriched
TeO2
Rodin et al.
Civitarese
Suhonen
new calculation 50
599
411
1085
1519
Nucl. Phys. A
729, 867 (2003) 37
434
575
S. Pascoli, S. T. Petcov and T. Schwetz, hep-ph/
500 meV
Counts / y ton Ge
natural
enriched
TeO2
Rodin et al.
new calculation
Civitarese
Suhonen
Nucl. Phys. A
729, 867 (2003)
0.51
5.99
4.11
10.85
0.37
4.3
5.7 15
50 meV
Sensitive masses at the 1 ton scale are required
15 meV
new calculation
Counts / y ton Ge
natural
enriched
TeO2
Rodin et al.
Civitarese
Suhonen
Nucl. Phys. A
729, 867 (2003)
0.046
0.54
0.033
0.39
0.37
0.98
0.52
1.37
As the future milestones are very challenge than the technology of future experiments have to be largely improvable and expandable!
The order magnitude of the Bkg is ≤ 1 c / y ton

5. 130Te as Source of Double Beta Decay
Cuoricino and CUORE experiments are using 130Te as source of the 0nDBD  why 130Te?
high natural isotopic abundance (33.87 %)
Isotopic abundance (%)
48Ca
76Ge
82Se
96Zr
100Mo
116Cd
130Te
136Xe
150Nd 20 40
Transition energy (MeV)
48Ca
76Ge
82Se
96Zr
100Mo
116Cd
130Te
136Xe
150Nd 2 3 4 5
Sensitivities higher than 1026 y imply 1028 – 1029 nuclides
A few percent of isotopic abundance is unacceptable
high transition energy (Q = 2530 keV)
this means large phase space for the decay
the Q-value is important with respect to the natural
radioactive background C E
2382
2530
2615
natural g background stops at 2615 keV
(208TI, Th chain) but 130Te is in a lucky position:
- outside the 238U background
- between the full energy and the compton
edge of 2615 keV photon

6. In a monolithic thermal model:
The Bolometric Technique
In a monolithic thermal model:
thermal signal
Heat sink
DT = E/C
Thermal coupling
The detector has to work at low temperature (10 mk) in order to develop high pulses
Thermometer
incident
particle
Crystal absorber

7. The Bolometric Technique
5 cm
Heat sink
Cu holder
Thermal coupling
Teflon
pieces
Thermometer
NTD
sensor
incident
particle
TeO2
cristal
Crystal absorber

8. Underground National Laboratory
Cuoricino experiment
Cuoricino experiment is installed in
Underground National Laboratory
of Gran Sasso
L'Aquila – ITALY
the mountain providing a 3500 m.w.e. shield against cosmic rays
CUORE
(hall A)
Cuoricino
(hall A)
R&D final tests for CUORE (hall C)

9. Cuoricino Detector
The Cuoricino detector has a tower-like structure and contains
44 TeO2 crystals 5x5x5 cm TeO2 crystals 3x3x6 cm3
The first ones are displaced in 4 crystal modules while the other ones are displaced in 2 planes of 9 crystal modules (11th and 12th planes). The total detector weight is 41 kg.
It is a self-consistent experiment that is giving significant results on 0n Double Beta Decay.

10. Some Pictures

11. Detector Performances
3x3x6 cm3 crystals
5x5x5 cm3 crystals
FWHM [keV] of the 2615 keV gamma line of 208Tl
(calibration with a 232Th source ~ 3 days)
average 5x5x5 cm3 crystals ~ 7 keV
average 3x3x6 cm3 crystals ~ 9 keV
2615 keV 208Tl
spectrum obtained
with a calibration
The calibration is performed periodically (every 2 weeks) using a mixed U and Th source placed outside the cryostat but inside the external lead shield

12. Average FWHM resolution
Cuoricino results
60Co sum peak
2505 keV
~ 3 FWHM from
DBD Q-value
MT = kg 130Te  y
Bkg = 0.18±0.02 c/keV/kg/y
Average FWHM resolution
for 790 g detectors: 7 keV
130Te
0nbb
t1/20n (y) > 3.0  1024 y (90% c.l.)
Mbb < 0.20 – 0.98 eV

13. 19 CUORICINO-like towers
CUORE Experiment
Array of 988 detectors:
19 Cuoricino-like towers.
M = ton of TeO2
M = 600 kg of Te
M = 203 kg of 130Te
90 cm
19 CUORICINO-like towers

14. ITALY U. S. A. CUORE Collaboration INFN Sezione di Milano
Dipartimento di Fisica dell'Università di Milano-Bicocca e Sezione di Milano Bicocca dell'INFN
Dipartimento di Fisica e Matematica dell'Università dell'Insubria
Dipartimento di Ingegneria Strutturale del Politecnico di Milano
Dipartimento di Fisica dell'Università di Roma La Sapienza e Sezione di Roma dell'INFN
Laboratori Nazionali del Gran Sasso (LNGS)
Laboratori Nazionali di Legnaro
Dipartimento di Fisica dell'Universita' di Genova e Sezione di Genova dell'INFN
Laboratory of Nuclear and High Energy Physics, University of Zaragoza
SINAP-CAS, Shanghai
Materials Science Division, Lawrence Berkeley National Laboratory
Nuclear Science Division, Lawrence Berkeley National Laboratory
Department of Physics, University of California, Berkeley
Department of Nuclear Engineering, University of California, Berkeley
Department of Materials Science and Engineering, University of California, Berkeley
Lawrence Livermore National Laboratory
Department of Physics and Astronomy, University of California, Los Angeles
California Polytechnic State University, San Luis Obispo
Department of Physics and Astronomy, University of South Carolina,
University of Wisconsin, Madison
ITALY
U. S. A.

15. CUORE Project Status CUORE data taking is foreseen in 2011
CUORE has a dedicated site in LNGS and the construction will start soon
The CUORE refrigerator is fully funded and has already been ordered
1000 crystals are fully funded by INFN and DoE
CUORE data taking is foreseen in 2011

16. General milestone for CUORE-0 assembly Dec 2008 - data taking Mar 2009
It’s the first step of CUORE:
The first tower of CUORE
It will be installed in Hall A of LNGS (replace Cuoricino)
52 TeO2 crystals (5x5x5 cm3 – 750 g)
5 x Te nuclei
Main reasons for CUORE-0
• test of assembly procedures
• check of CUORE background
• test of CUORE-collaboration
• incentive in view of CUORE schedule
General milestone for CUORE-0
assembly Dec data taking Mar 2009

17. CUORE Sensitivity Mbb < 11 – 60 meV Mbb < 20 – 100 meV
The first generation of experiments was mainly devoted to the proof of the technology.
CUORE is a second generation experiment with the possibility of exploring part of the inverted hierarchy
F0n = 9.2 ´ 1025 ´ ( T [ y ] )1/2
F0n = 2.9 ´ 1026 ´ ( T [ y ] )1/2
5 y sensitivity (1 s) with feasible
assumption: b = 0.01 counts/(keV kg y)
FWHM = 10 keV
5 y sensitivity (1 s) with aggressive
assumption: b = counts/(keV kg y)
FWHM = 5 keV
Mbb < 20 – 100 meV
Mbb < 11 – 60 meV

18. CUORE and the Inverse Hierarchy region
Mbb band corresponding to the inverted hierarchy
band of 130Te half lives
Nuclear models
T1/2 x 1026 y for 130Te
QRPA Tuebingen et al.
Shell Model
QRPAJyväskylä et al.
Nuclear models
CUORE
Aggressive
(5 y)
CUORE_
conservative
(5 y)

19. The Cuoricino background model
To understand the critical point of CUORE we can use what we have learned by Cuoricino results
214Bi
60Co
p.u.
208Tl
MC: the background in CUORICINO is due to degraded alpha’s which release only a part of their energy in the detector (surface contamination)
TeO2 Cu

20. CUORE background model
The sources of the background
Radioactive contamination in the detector materials (bulk and surface)
Radioactive contamination in the set-up, shielding included
Neutrons from rock radioactivity
Muon-induced neutrons
Monte Carlo simulation of the CUORE background based on:
CUORE baseline structure and geometry
Gamma and alpha counting with HPGe and Si-barrier detectors
Cuoricino experience  Cuoricino background model
Specific measurements with dedicated detectors in test refrigerator in LNGS
Results…..

21. The only limiting factor
CUORE background components
Background in DBD region
( 10-3 counts/keV kg y )
Component
Environmental gamma
< 1
Apparatus gamma
< 1
The only limiting factor
Crystal bulk
< 0.1
Crystal surfaces
< 3
Close-to-det. material bulk
< 1
Close-to-det. material surface
~ 20 – 40
Neutrons
~ 0.01
Muons
~ 0.01

22. Strategies for the control of surface background
(A) Passive methods  surface cleaning
(B) Active methods ( “reserve weapons” and diagnostic) events ID
Mechanical action
Chemical etching / electrolitical processes
Passivation
 surface sensitive bolometers
scintillating bolometers able
to separate a from electrons

23. Fast high and saturated pulse
Example of R&D detectors for bkg reduction
Surface Sensitive Bolometers:
The idea is to use auxiliary thin Ge bolometers to control surface contamination
TeO2 thermistor DV
If we make a scatter plot of the pulse amplitude (pulse amplitude obtained with thermistor on Ge crystal versus those obtained with thermistor on TeO2 crystal) we obtain two well separated behaviours
Classical pulse
Classical pulse
Classical pulse
Fast high and saturated pulse

24. first prototypes at Insubria University
Pictures of Surface Sensitive Bolometers
new test at LNGS
first prototypes at Insubria University

25. Example of experimental scatter plot with SSB
pulses due to events in the Ge-absorber
Pulses due to events in the TeO2-absorber
alfa peaks
212Po
216Po
220Ra
224Ra

26. CUORE-next A big improvement in sensitivity could be obtained by:
The CUORE technology is very promising because is largely improvable and expandable!
A big improvement in sensitivity could be obtained by:
Using the enrichment option: change the Te with “all 130Te”
 factor 3 in Mass
Using scintillating crystals with a double read-out for a full suppression of gamma – alpha background (scintillating + high Q-value nuclei)
 strong reduction of the Background
Using a smarter, yet more complex, background rejection system
 going to c/kg/y/keV

27. Conclusions
Bolometers represent a well established technique, very competitive for
neutrinoless DBD search
Cuoricino is presently the most sensitive 0nDBD running experiment, and it demonstrates the feasibility of a large scale bolometric detector (CUORE) with high energy resolution and competitive background
CUORE, a next generation detector, is funded and will start to take
data during the 2011
In case of 0nDBD evidence confirmation the new era of the precise measurement of 0nDBD would start and the bolometric technique will allow the measurement of different nuclei as source of the decay. This is fundamental to reduce uncertainties in nuclear matrix elements.
CUORE technology is very promising for further steps in the 0nDBD search

31. General milestone for CUORE-0 assembly Dec 2008 - data taking Mar 2009
Crystals In our hands in August 2008 (first 28) and in September 2008 (second 28)
Validation of the first bacth: Hall C run in June-August 2008
Thermistors and heaters Decision on the size of the flat-pack thermistors: Mar 2008
Dedicate April-May 2008 to production
Tower design Final technical drawing ready in December 2007
Copper Production of copper parts: February- April 2008
All copper parts ready in April 2008
Cleaning copper parts: May – October 2008
Clean room preparation Borexino clean room ready to use in July 2008
Packaging and storage Storage system ready in April 2008
Assembly CUORE-0 tower assembled in December 2008
Tower storage Storage and transportation ready in December 2008
Tower-cryostat interface Interface ready in December 2007
 Cleaning (UTECM): May – Oct 2008

32. CUORE – Background Model
TeO2 Bulk contamination
from the visible peaks and assuming secular equilibrium crystal bulk contaminations have been evaluated
232Th => (2 +/- 0.4) x g/g
238U => (1.0 +/- 0.2) x g/g
210Pb => (8 +/- 1) x 10-6 Bq/kg
Contribution to CUORE DBD bkg
(Montecarlo simulation)
~ 10-4 c/keV/kg/y
Surface contaminations:
CUORICINO DBD bkg: ± 0.01 c/keV/kg/y =
30 ± 5 % 232Th in cryostat
20 ± 5 % TeO2 Surface
50 ± 10 % Cu Surface
Selected and optimized shields
Factor ~ 5 reduction in TeO2 cont.
Factor ~ 1.8 reduction in Cu cont.
New structure geometry
(~ 1/2 Cu facing crystals)
negligible cryostat contribution
~ 7·10-3 c/keV/kg/y
~ 2.5·10-2 c/keV/kg/y

33. The Cuoricino background and the surface radioactivity model
Gamma region
214Bi
60Co
p.u.
208Tl
~ 0.11 c / keV kg y

34. Reconstruction of the Cuoricino spectrum
in the region 2.5 – 6.5 MeV
Additional
component required
here
0nDBD

35. The additional component: inert material surface contamination
In order to explain the MeV region BKG, one has to introduce
238U or 210Pb surface contamination of the copper structure facing the detectors

36. Reduction of surface radioactivity
(passive methods)
Elimination of the background source
Crystal surface:
reduction of factor 5 of crystal surface contamination respect to Cuoricino by using ultra-pure HNO3 and lapping with ultra-pure powder
Copper surface:
reduction of factor between 2 and 3 of copper surface contamination respect to Cuoricino in a Hall C bolometric test where the copper frame were covered with about 100mm of polyethylene multilayer.
for CUORE copper we will use the following procedure:
- Mechanical barrel polishing by Tumbling
- Removal of 100 micron by electropolishing
- Removal of tenths of microns by Chemical Etching
- Removal of few microns by Magnetron Sputtering in UHV (Plasma Cleaning)
- Removal on nanometric scale by Ion Beam Cleaning in UHV
Bolometric test on small components of Cuoricino/CUORE detector
in order to see if they could be dangerous in CUORE
our present best background MeV region -> 0.03 c/keV/kg/y in CUORE

37. Can Cuoricino scrutinize the HM claim of evidence?
Cuoricino and the HM claim of evidence
Evidence of 0nDBD decay claimed by a part of the Heidelberg-Moscow experiment (Klapdor et al.) in the nuclide 76Ge
T1/20v (y) = ( )  1025 (3σ range)
Klapdor et al.
Physics Letters B 586 (2004)
Best value: 1.19x1025 y
mββ= 0.24 – 0.58 eV (3σ range)
Nuclear matrix element of Muto-Bender-Klapdor
Can Cuoricino scrutinize the HM claim of evidence?

38. Comparison of experimental results in a given nuclear model
(T0n1/2)-1 = G0n |M0n|2 Mbb 2
T1/20v
(Klapdor et al.)
Choose a nuclear model
T1/20v (130Te) 2 / 1
130 76 ) ( v Ge Te M G
Klapdor T × =
QRPA Tuebingen-Bratislava -Caltech group: erratum of nucl-th/
QRPA Jyväskylä group: nucl-th/
Shell Model: Poves’ 4th ILIAS Annual Meeting - Chambery
For the nuclear models, consider three active schools of thoughts:

39. Cuoricino and the 76Ge claim of evidence
The HM claim half life range (3s) is converted into a corresponding range for 130Te using the three mentioned models
3x1024 y
Present limit
7x1024 y
Final sensitivity
Nuclear models
QRPA Tuebingen et al.
Shell model
QRPA Jyväskylä et al.
T1/2 x 1024 y for 130Te

40. Experimental Requirements
sum electron energy / Q
F0n 
M T
b G
1/2
Lifetime sensitivity F0n corresponds to the minimum number of detectable events above background at a given C.L.
M = Mass  large amount of source nuclei (ton scale)
T = Time  long time measurement
b = Background  radioactive clean material and underground location
G = Energy resolution  good detector performances