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CUORE & CuoricinoA Search for Neutrinoless Double Beta Decay
Reina MaruyamaFor CUORE & Cuoricino Collaboration
LBNL / University of Wisconsin, Madison
NNN 2006, Seattle, WASeptember 21 - 23, 2006
R.H. MaruyamaNNN 2006, Seattle, WA
Bolometric 0νββ Experiments: Past & Future
Cuoricino: Currently the largest bolometer & most sensitive 0νββ experiment runningCUORE: Next generation with 741 kg of TeO2 (204 kg of 130Te)
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Mas
s [k
g] Cuoricino
MiDBD
4 detectors array340 g
73 g
1985 1990 1995 2000 2005 2010 2015
CUORE
Phys. Lett. B, 285 (1992) 176
Phys. Lett. B, 335 (1994) 519
Phys. Lett. B 557 (2003)167
hep-ex/0501010
Phys. Rev. Lett. 95 (2005) 142501
R.H. MaruyamaNNN 2006, Seattle, WA
Tellurium-130
High natural isotope abundance of 33.8%: No enrichmentQ = 2530 keV
– Large phase space– Low background: above most U/Th γ’s, between 232Th Compton edge
(2360 keV) and full γ (2615 keV)Geo-chemical measurements: T2νββ
1/2 = (0.7 - 2.7) x 1021 yMiDBD: T2νββ
1/2 = (6.1± 1.4 (+2.9 - 3.5)) x 1020 y
High natural isotope abundance of 33.8%: No enrichmentQ = 2530 keV
– Large phase space– Low background: above most U/Th γ’s, between 232Th Compton edge
(2360 keV) and full γ (2615 keV)Geo-chemical measurements: T2νββ
1/2 = (0.7 - 2.7) x 1021 yMiDBD: T2νββ
1/2 = (6.1± 1.4 (+2.9 - 3.5)) x 1020 y
Rodin nucl-th/0503063
R.H. MaruyamaNNN 2006, Seattle, WA
Cryogenic Bolometers for 0νββ Experiments
Heat sink
Thermal couplingThermometer
Incident particle(Energy → ΔT)
Crystal absorber
Detector = Source– Maximize source mass– minimize background
Energy measured thermally– Measurable temperature change– Energy fully detected
Excellent energy resolution– 5 keV @ 2.5 MeV
Multiple material choices– 130TeO2, 48CaF2, 76Ge, 100MoPbO4,
116CdWO4 (150NdF3 150NdGaO3) Requires low temperature
– Low heat capacity necessary fordetectable temperature change
No event-type discrimination– R&D underway (SSB, scintillation)
CUORE module model
R.H. MaruyamaNNN 2006, Seattle, WA
For E = 1 MeV:ΔT = E/C ≅ 0.1 mKSignal size: 1 mV
Time constant: τ = C/G = 0.5 s
Energy resolution (FWHM): ~ 5-10 keV at 2.5 MeV
Heat sink: Cu structure (8 mK)Thermal coupling: Teflon (G = 4 pW/mK)Thermometer: NTD Ge-thermistor (dR/dT ≅ 100 kΩ/µK)Absorber: TeO2 crystal (C ≅ 2 nJ/K ≅ 1 MeV / 0.1 mK)
Heat sink: Cu structure (8 mK)Thermal coupling: Teflon (G = 4 pW/mK)Thermometer: NTD Ge-thermistor (dR/dT ≅ 100 kΩ/µK)Absorber: TeO2 crystal (C ≅ 2 nJ/K ≅ 1 MeV / 0.1 mK)
TeO2 Bolometer: Source = DetectorTeO2 Bolometer: Source = Detector
CUORE/Cuoricino Bolometer
Single pulse example
Time (ms)
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plitu
de (a
.u.)
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R.H. MaruyamaNNN 2006, Seattle, WA
Total detector mass: 40.7 kg ⇒ 11.64 kg 130TeTotal detector mass: 40.7 kg ⇒ 11.64 kg 130Te
Cuoricino
11 modules, 4 detector each,crystal dimension: 5x5x5 cm3
crystal mass: 790 g44 x 0.79 = 34.76 kg of TeO2
2 modules x 9 crystals eachcrystal dimension: 3x3x6 cm3
crystal mass: 330 g9 x 2 x 0.33 = 5.94 kg of TeO2
(2 enriched in 128Te @82.3%)(2 enriched in 130Te @75%)
Shielding:• Cu box + Roman Pb inside cryostat• 20 cm Pb & 10 cm borated polyethylene outside
R.H. MaruyamaNNN 2006, Seattle, WA
Projected Cuoricino Sensitivity
<m> range from various QRPA calculations:Rodin, Faessler, Simkovic, & Vogel Nucl. Phys. A 766 107 (2006)Staudt, Kuo & Klapdor-Kleingrothaus, PRC 46 871 (1992)
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T 1/20ν
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sitiv
ity [1
024 y
ears
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1086420Running Time [years]
CUORICINO (bkgd = 0.18 cnts/keV*kg*yr)3 yr sensitivity = 6.3 x 1024 yrs
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<mν>
[eV]
1086420Running Time [years]
CUORICINO (bkgd = 0.18 cnts/keV*kg*yr)
<mν> sensitivity from QRPA Calculations
Projected sensitivity of Cuoricino (1σ)
€
T1/ 20ν = ln2 ⋅ NA (det.efficiency)(isotopic.abundance)
mol.mass(detector.mass)(time)(bkgd)* (resolution)
60% live time for 3 yrs = 4 x1024 yrs (90% CL)
R.H. MaruyamaNNN 2006, Seattle, WA
Cuoricino Results
Total Exposure: 8.38 kg-y of 130TeBKG: 0.18 ± 0.01 cnts/(keV-kg-y)FWHM at 2615 keV: ~ 8 keV
April 2003 - May 2006
R.H. MaruyamaNNN 2006, Seattle, WA
CUORE
Array of 988 TeO2 crystals 19 Cuoricino-like towers 4 crystals x 13 levels per tower 5x5x5 cm3 (750 g each) 130Te: 33.8% isotope abundance 741 kg TeO2 ⇒ 204 kg 130Te
Goalbackground < 0.01 cnts/keV/kg/y
Resolution = 5 keV5 year sensitivityF0ν > 2.1 x1026 y
mee < ~ 19 – 100 meV
Goalbackground < 0.01 cnts/keV/kg/y
Resolution = 5 keV5 year sensitivityF0ν > 2.1 x1026 y
mee < ~ 19 – 100 meV
(approved by INFN and the Science Council of Gran Sasso Laboratory)
R.H. MaruyamaNNN 2006, Seattle, WA
CUORE Sensitivity
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T 1/20ν
Sen
sitiv
ity [1
026 y
ears
]
1086420Running Time [years]
CUORE (bkgd = 0.001 cnts/keV*kg*yr) CUORE (bkgd = 0.01 cnts/keV*kg*yr)
5 yr sensitivity = 6.5 x 1026 yrs
5 yr sensitivity = 2.1 x 1026 yrs
Projected sensitivity of CUORE (1σ)400
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0<m
ν> [m
eV]
1086420Running Time [years]
CUORE bgd = 0.01 cnts/keV*kg*yr CUORE bgd = 0.001 cnts/keV*kg*yr
<mν> sensitivity from QRPA Calculations
* <m> range from various QRPA calculations:high: Rodin, Faessler, Simkovic, & Vogel Nucl. Phys. A 766 107 (2006)low: Staudt, Kuo & Klapdor-Kleingrothaus, PRC 46 871 (1992)
R.H. MaruyamaNNN 2006, Seattle, WA
Two dilution refrigerators:Hall A: CUORICINO
CUORE: next to Cuoricino Hall C (R&D final tests for CUORE)
Gran Sasso National Underground Laboratory
Site for CUORE approved in Hall AWork began to prepare space
Overburden at LNGS: 3200 m.w.e
R.H. MaruyamaNNN 2006, Seattle, WA
CUORE Site in Hall A at LNGS
Feb. 2006
CRESST
CUORE
Feb. 2006
Mar. 2006
R.H. MaruyamaNNN 2006, Seattle, WA
CUORE Housing and Cryostat Design
R.H. MaruyamaNNN 2006, Seattle, WA
Designing CUORE
Use knowledge gained from Cuoricino, simulations, and R&D in Hall C– Custom designed cryostat & Shielding
• Need to accommodate the required shielding inside• Clean materials selected for dewars & shields• Improve reliability for higher live-time
– Radioactive background reduction• Select materials and cleaning procedures using tests in Hall C, HPGe
counting, ICPMS, NAA, etc.– e.g.Raw Te, NTD Ge Thermistors, copper structure, crystal surfaces, …
• Simulations of possible backgrounds from environment (neutrons etc.)• Proton activation studies indicate crystals must go underground in < 4months
– New detector structure design• Vibration isolation and detector suspension• Structure designed to minimize surfaces and vibration modes• Uniform and better energy resolution among detectors• Ease of assembly
R.H. MaruyamaNNN 2006, Seattle, WA
Cuoricino Background in the 0νββ Region
30 ± 10% from 208Tl (2615 keV) Compton events from Th in cryostat shields10 ± 5% from α‘s from U/Th on crystal surfaces50 ± 20% from α‘s from U/Th, mainly from copper surfaces
214Bi 0νββ
Flat b.g. from α’s
Cuoricino background (2520 - 2590 keV): 0.18 ± 0.01 cnts/(keV-kg-y)
R.H. MaruyamaNNN 2006, Seattle, WA
Backgrounds: Cuoricino to CUORE
CuoricinoHall C
α source studies from Cuoricino, series of tests in Hall C, &Monte Carlo
• < 2.6 MeV: Higher rates due to higher γ rates in Hall C cryostat than in Cuoricino.Possible to study α backgrounds only.
• > 3 MeV: Significant reduction shown• Tested items: cleaning procedures, mounting schemes, structure design, material
selections• Factor of 4 reduction seen in crystal surface contamination, ~2 in Cu surfaces• More tests underway to reach goal of < 0.01 c/keV/kg/yr
Comparison of Cuoricino and Hall C measurements
R.H. MaruyamaNNN 2006, Seattle, WA
Monte Carlo simulation for CUORE:Use background levels measured in CUORICINO, HPGe counting, R&Din Hall C, ICPMS, neutron activation analysis etc.
Expected Backgrounds in CUORE
~ (2-4) x 10-2Inert surfaces (e.g. Cu structure, shields)
< 10-3Outside inner Pb shield (environmental, cryostat,induced n’s…)
< 10-3Internal Pb shield & Cu structure bulk
< 10-3Small parts (NTD Ge, PTFE, Au wires…)
Expected background(cnts/keV/kg/yr)
Source
~ 10-42νββ
< 3 x 10-3TeO2 Surface (Hall C: measurement)
< 10-4TeO2 Bulk (Hall C: measurement)
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R.H. MaruyamaNNN 2006, Seattle, WA
Cuoricino Shielding
R.H. MaruyamaNNN 2006, Seattle, WA
CUORE ShieldingRoman lead (210Pb < 4mBq/kg)
– ~15 cm layer directly above detector– ~3 cm layer immediately around
detectorLow activity lead
– Two disks above detector, at 50 mKand 600 mK, both 10 cm thick.
– 16 Bq/kg of 210Pb inner layer (~10cm)– 150 Bq/kg outer layer (~10cm)
Borated polyethylene box– most neutrons eliminated w/ ~10 cm– hermetically sealed & flushed with N2
to exclude radon– Simulation shows no measurable
background contribution in DBD regionFaraday cage
– Important for near-threshold events
R.H. MaruyamaNNN 2006, Seattle, WA
CUORE Detector Energy Resolution
CUORE Goal: 5 keV @ 2500 keV• Cuoricino’s best: 3.9 keV @ 2615 keV• All crystals: 9 keV average• 5x5x5 cm3 crystals: 7 keV average• Improvements
– Production of uniform thermistors– Uniform thermal coupling of crystal to thermistor– Better design of crystal holders– Improved gain stabilization through heater pulses
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Energy resolution FWHM
Column SColumn T
5 10 15 20 30 FWHM [keV]
num
ber o
f det
ecto
rs
3x3x6 cm3
crystals
5x5x5 cm3 crystals
Resolution: 5x5x5 cm3 crystal0.8 keV FWHM @ 46 keV1.4 keV FWHM @ 351 keV2.1 keV FWHM @ 911 keV2.6 keV FWHM @ 2615 keV (.1%)3.2 keV FWHM @ 5407 keV
Resolution: 5x5x5 cm3 crystal0.8 keV FWHM @ 46 keV1.4 keV FWHM @ 351 keV2.1 keV FWHM @ 911 keV2.6 keV FWHM @ 2615 keV (.1%)3.2 keV FWHM @ 5407 keV
R.H. MaruyamaNNN 2006, Seattle, WA
NTD Ge Thermistors
Neutron Transmutation Doped Ge Thermistors• Developed at Berkeley by E.E. Haller (material science)
Ge doped with Ga & As by neutron irradiation• provides very uniform doping• Few % variation in doping results in performance variation
Reliable, reproducible, and stable, Good energy resolutionIrradiation for CUORE thermistors underway
Neutron Transmutation Doped Ge Thermistors• Developed at Berkeley by E.E. Haller (material science)
Ge doped with Ga & As by neutron irradiation• provides very uniform doping• Few % variation in doping results in performance variation
Reliable, reproducible, and stable, Good energy resolutionIrradiation for CUORE thermistors underway
Nominal neutron dose 4x1018 n/cm2
Nominal concentrations Ga: 1 x 1017 /cm3
As: 3 x 1016 /cm3
Se: 2 x 1015 /cm3
Nominal neutron dose 4x1018 n/cm2
Nominal concentrations Ga: 1 x 1017 /cm3
As: 3 x 1016 /cm3
Se: 2 x 1015 /cm3
Ge70 Ge71 Ge72 Ge73 Ge74 Ge75 Ge76 Ge77
11.4dGa71
As75 As77
Se77
11.3 hr
39 hr
β
EC
β
β
1.38 hr
Acceptor
Donor
Double Donor
NTD Process:NTD Process:
R.H. MaruyamaNNN 2006, Seattle, WA
A composite bolometer with a thin crystal of TeO2
Surface event on SSB thermistor
Bulk event on bulk thermistor
Surface event on bulk thermistor
Bulk event on SSB thermistor
Beyond CUORE
Enriched crystals for increased sensitivityOther Isotopes (CaF2, Ge, PbMoO4, CdWO4) Possible event discrimination in bolometers• Scintillating Crystals: use both heat and light for b.g. rejection• Surface Sensitive Bolometers (SSB)
R.H. MaruyamaNNN 2006, Seattle, WA
Rise-time distribution(SSB thermistor) Fast surface events
Slow bulk events
Beyond CUORESurface Sensitive Bolometer Tests with Ge(tests of SSB with TeO2 underway in Gran Sasso)
R.H. MaruyamaNNN 2006, Seattle, WA
Conclusion
• Cryogenic bolometers– good efficiency & high resolution– low radioactive backgrounds
• Cuoricino– running since April 2003– great prototype and R&D for CUORE– will continue to set new limits until CUORE starts
• CUORE– designed to probe inverse hierarchy– technology in place and tested as Cuoricino– background studies well underway
• Future…– isotope enrichment– modular design allows for multiple isotope search– further background reduction w/ hybrid detectors
CUORE Collaboration
Universita’ di Milano-Bicocca - INFN Sezione diMilano
F. Alessandria, R. Ardito1 , C. Arnaboldi, C. Brofferio, S. Capelli, L.Carbone, M. Clemenza, O. Cremonesi, E. Fiorini, C. Nones,A. Nucciotti, M. Pavan, G. Pessina, S. Pirro, E. Previtali, M.
Sisti, L. Torres, L. Zanotti
Politecnico de MilanoG. Maier
Laboratori Nazionali del Gran SassoM. Balata, C. Bucci, S. Nisi
Universita’ di Firenze e INFN, FirenzeM. Barucci, L. Risegari, G. Ventura
University of ZaragozaS. Cebrian, P. Gorla, I.G. Irastorza
Universita’ dell’Insubria e Sezione di Milano dell’INFN,Como
A. Giuliani, M. Pedretti, S. Sangiorgio
Universita di GenovaS. Cuneo, S. Didomizio, A. Giachero, E. Guardincerri, M. Olcese,
P. Ottonello, M. Pallavicini
Laboratori Nazionali di LegnaroV. Palmieri
Universita di RomaF. Bellini, C. Cosmelli, I. Dafinei, M. Diemoz, F. Ferroni,
C. Gargiulo, E. Longo, S. Morganti, M. Vignati
University of California at BerkeleyM.P. Decowski2 , M.J. Dolinski3 , S.J. Freedman2,
Yu.G. Kolomensky2, E.E. Haller2
University of South CarolinaD.R. Artusa, F.T. Avignone III, I. Bandac, R. J. Creswick, H.A.
Farach, C. Rosenfeld
Lawrence Berkeley National LaboratoryJ.W. Beeman, R.W. Kadel, A.R. Smith, N. Xu
Lawrence Livermore National LaboratoryE.B. Norman
University of California, Los AngelesH. Huang, C. Whitten Jr.
University of Wisconsin, MadisonK.M. Heeger4 , R.H. Maruyama4
California Polytechnic State UniversityT.D. Gutierrez4
2also at LBNL3also at LLNL
4 currently at LBNL