CUORE & Cuoricino - University of...

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)

0,01

0,10

1,00

10,00

100,00

1000,00

10000,00

Year

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


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


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


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)

Am

plitu

de (a

.u.)

1000 2000 3000 4000


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


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)

10

8

6

4

2

0

T 1/20ν

Sen

sitiv

ity [1

024 y

ears

]

1086420Running Time [years]

CUORICINO (bkgd = 0.18 cnts/keV*kg*yr)3 yr sensitivity = 6.3 x 1024 yrs

1.4

1.2

1.0

0.8

0.6

0.4

0.2

<mν>

[eV]


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)


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


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)


CUORE Sensitivity

8

6

4

2

0

T 1/20ν

Sen

sitiv

ity [1

026 y

ears

]


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

300

200

100

0<m

ν> [m

eV]


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)


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


CUORE Site in Hall A at LNGS

Feb. 2006

CRESST

CUORE

Feb. 2006

Mar. 2006


CUORE Housing and Cryostat Design


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


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)


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


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)

√√√

√

√√


Cuoricino Shielding


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


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

0123456789

10111213141516

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


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:


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)


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)


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

CUORE & Cuoricino - University of...

Documents

Transcript of CUORE & Cuoricino - University of...