LUCIFER Low background Underground Cryogenic Installation For - - PowerPoint PPT Presentation

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LUCIFER Low background Underground Cryogenic Installation For - - PowerPoint PPT Presentation

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LUCIFER Low background Underground Cryogenic Installation For Elusive Rates Marco Vignati INFN Roma NPB 2012, Shenzhen, 24 Sept. 2012 Bolometric searches of 0 DBD Bilenky and Giunti, 2012 1 CUORICINO: Current Bound 11kg 130 Te bkg = 0.17

slide-1
SLIDE 1

Marco Vignati INFN Roma NPB 2012, Shenzhen, 24 Sept. 2012

LUCIFER

Low background Underground Cryogenic Installation For Elusive Rates

slide-2
SLIDE 2

mmin [eV] |m| [eV]

NS IS

Cosmological Limit Current Bound

104 103 102 101 1 104 103 102 101 1

1 2 3

Bolometric searches of 0νDBD

2

KK evidence -76Ge

Bilenky and Giunti, 2012

CUORICINO: 11kg 130Te bkg = 0.17 c/keV/kg/y CUORE: 206kg 130Te bkg ~ 1·10-2 c/keV/kg/y Needs: 1 ton isotope bkg < 10-3 c/keV/kg/y

slide-3
SLIDE 3

CUORICINO

  • MC: most of the background in CUORICINO is due to degraded α

particles which release only a part of their energy in the detector (surface contaminations, mainly in copper).

  • TeO2 bolometers, per se, do not allow to discriminate β and α

particles.

  • α bkg partially reduced by cleaning the detector parts.
  • β/γ smaller in CUORE thanks also to the self-shielding geometry.

CUORE: the α nightmare

3

α’s

TeO2 TeO2 Cu

slide-4
SLIDE 4

Scintillating bolometers

  • Scintillating crystals can be operated as bolometers. Unfortunately

TeO2 does not scintillate, other compounds must be considered.

  • The simultaneous read-out of light and thermal signals allows to

discriminate the α background thanks to the scintillation yield different from β particles.

4

Thermistor Bolometer Energy Release Light detector

slide-5
SLIDE 5
  • 0νDBD candidates of experimental interest:
  • In general, Q > 2615 keV isotopes

are preferred because they lie above the natural radioactivity edge.

  • However the choice has been

dominated so far by technology compromises.

130Te 76Ge 100Mo 116Cd 82Se

136Xe

U and Th environmental bkg

5

Isotope choice .

(arXiv:1201.4916)

slide-6
SLIDE 6

Light detectors

  • Germanium disks (5 cm diameter, 0.1-1 mm thick).
  • Calibration with a 55Fe source: 5.9 & 6.5 keV X-rays.
  • ΔE @55Fe: ~ 130 eV RMS
  • ΔE @baseline: 100 eV RMS

6

slide-7
SLIDE 7

Candidate #1: ZnSe

7

DBD Isotope: Q-value [keV] isotopic abundance Light Yield [keV/MeV] QF

82Se

2995 9% 7-11 4

Largest crystal

  • perated so far: 431g
slide-8
SLIDE 8

Detected Light [keV] 50 100 150 200 250 300 350 400 Light Decay Time [ms] 7 8 9 10 11 12 13 14

β/γ-background α-crystal contamination

Energy [keVee]

1000 2000 3000 4000 5000 6000 7000 8000

Light Yield [keV/MeV]

5 10 15 20 25 30 35 40

ZnSe

  • QF > 1 is odd:
  • Observed only in this

compound (CdWO4 ZnMoO4 and other crystals have QF < 1).

  • not understood.

8

0νDBD

  • Excellent separation

using light energy and signal shape

Light decay-time [ms]

slide-9
SLIDE 9

Integral 101 / ndf

2

  • 8.021 / 14

A 1.9 ± 13 mean 0.6 ± 2615

  • 0.594

± 5.741

Decorrelated energy [keVee]

2590 2600 2610 2620 2630 2640

counts / 2 keVee

2 4 6 8 10 12 14 16

Integral 101 / ndf

2

  • 8.021 / 14

A 1.9 ± 13 mean 0.6 ± 2615

  • 0.594

± 5.741 Integral 101 / ndf

2

  • 4.035 / 13

A 1.5 ± 10.5 mean 1.0 ± 2614

  • 1.116

± 7.938

Energy [keVee]

2590 2600 2610 2620 2630 2640 2 4 6 8 10 12

Integral 101 / ndf

2

  • 4.035 / 13

A 1.5 ± 10.5 mean 1.0 ± 2614

  • 1.116

± 7.938

Decorrelated energy [keVee]

2590 2600 2610 2620 2630 2640

Detected light [keV]

12 13 14 15 16 17 18 19 20 21

Energy [keVee]

2590 2600 2610 2620 2630 2640

Detected light [keV]

12 13 14 15 16 17 18 19 20 21 ZnSe: Light-Heat correlation

9

ΔE@2615 keV: 13 keV FWHM

slide-10
SLIDE 10
  • Operation of a tower of 32-40 Zn82Se crystals at LNGS.
  • Option1: use the Cuoricino cryostat in hallA (presently hosting

CUORE-0), if CUORE-0 stops in 2015.

  • Option2: use the cryostat in hallC (presently running the CUORE-0

and LUCIFER R&Ds). Needs cryostat update.

Cuoricino cryostat:

  • Inner shield:
  • 1cm Roman Pb

A (210Pb) < 4 mBq/Kg

  • External shield:
  • 20 cm Pb
  • 10 cm Borated

polyethylene

  • Nitrogen flushing to

avoid Rn contamination.

Plan for a ZnSe array in 2015

10

LUCIFER

4 crystals per floor

slide-11
SLIDE 11

ZnSe: schedule

11

2012 2013 2014 2015

Light detector R&D Thermistors prod. Crystal growth R&D

82Se prod. (15 kg)

Enriched crystals production Array assembly

The most crucial part is represented by the crystal growth. The supplier (Ukraine) is presently fine-tuning the complicate procedure (that starts with metal Zn and metal Se). The request of minimizing the 82Se waste is a complicate issue. The target is to reach > 75 % efficiency.

slide-12
SLIDE 12

Energy [keVee]

1500 2000 2500 3000 3500 4000

Light Yield [keV/MeV]

9 10 11 12 13 14 15

Do we need a μ-veto?

  • The event includes hits on close detectors (multi-site event)
  • Multiple γ’s produced by μ interactions in the materials close to

the detector.

  • Easy to remove in this case, but what if one has one hit only?
  • Montecarlo simulation under development.

12

ZnSe data: 1 β/γ event above the 2615 keV line in 580 hours ~ 5x10-2 counts/keV/kg/y

β/γ α

slide-13
SLIDE 13

Candidate #2: ZnMoO4

13

DBD Isotope: Q-value [keV] isotopic abundance Light Yield [keV/MeV] QF

100Mo

3034 10% 1.5 0.2

Largest crystal

  • perated so far: 330g
slide-14
SLIDE 14

ZnMoO4 .

14 Energy [keV]

500 1000 1500 2000 2500 3000 3500 4000 TVR [a.u.]

  • 14
  • 12
  • 10
  • 8
  • 6
  • 4
  • 2

2 4 Energy [keV] 500 1000 1500 2000 2500 3000 3500 4000 LY [keV/MeV] 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4

  • Eur. Phys. J. C 72 (2012) 2142

α source β/γ source α source β/γ source

0νDBD 0νDBD

Heat signal shape parameter Light Yield [keV/MeV]

Discrimination using the shape of the heat signal! Excellent discrimination using the light signal

slide-15
SLIDE 15

Entries 2821 Mean 2742 RMS 1449 Integral 2821

1 2 3 4 5 6 7 8 9 10

3

10 × 1 10

2

10

Po

Energy [keV] Counts / 9 keV

210 226Ra 222Rn

source Po

218

Bi Po

214 214

ZnMoO4

15

11528 1.153e+04

Energy [keV]

500 1000 1500 2000 2500

counts / 3 keV

10 20 30 40 50 60 70 80 90

Entries 11528

2.925

2590 2600 2610 2620 2630 2640 10 20 30 40 50 60 70

FWHM= 6.3 keV

Energy resolution similar to CUORICINO (2x better than ZnSe)

β/γ source

Internal contaminations:

232Th < 1.4 pg/g

slide-16
SLIDE 16

Simulated Čerenkov emission spectrum from 1.5 MeV γ in TeO2 at low temperatures. Simulated emitted Čerenkov light as a function of β/γ energy.

Candidate #3: TeO2

16

Photon Energy (keV) 500 1000 1500 2000 2500 Cherenkov light (eV) 100 200 300 400 500 600 700 800 900 1000

/ ndf 2
  • 3.723 / 5
Prob 0.5899 p0 1.143e-09 ±
  • 3.111e-08
p1 4.448e-06 ± 0.0001678 p2 0.00428 ± 0.1222 p3 0.8393 ±
  • 10.43
/ ndf 2
  • 3.723 / 5
Prob 0.5899 p0 1.143e-09 ±
  • 3.111e-08
p1 4.448e-06 ± 0.0001678 p2 0.00428 ± 0.1222 p3 0.8393 ±
  • 10.43

Produced Cherenkov light[eV]

867 eV 0νDBD

β/γ energy [keV]

m) µ (

  • 0.2

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

  • dN/d

100 200 300 400 500 600 700 800

dN/dλ [μm-1] λ [μm]

TeO2 does not scintillate, however MeV β’s emit Čerenkov light, unlike α’s [ T. Tabarelli de Fatis, Eur. Phys. J. C 65 (2010) 359].

slide-17
SLIDE 17

Heat energy [keV]

1000 2000 3000 4000 5000

Light energy [keV]

  • 0.3
  • 0.2
  • 0.1

0.1 0.2 0.3 0.4

/ ndf

2

  • 11.9 / 6

[keV]

th

E 64.47 ± 360.3 Yield [eV/MeV] 2.846 ± 48.33 / ndf

2

  • 11.9 / 6

[keV]

th

E 64.47 ± 360.3 Yield [eV/MeV] 2.846 ± 48.33

210Po-α

contamination β / γ s

  • u

r c e

Detected β/γ light: 48 eV/MeV 105 eV @2.527 MeV 0νDBD

Čerenkov from a CUORE crystal

17

  • Detected light not sufficient to discriminate α’s event by event.
  • Needs light detector development: light collection, energy resolution.
slide-18
SLIDE 18

Signal/Noise of light detector

1 2 3 4 5 6 7 8

y]

26

DBD sensitivity [10

  • 68% 0

2 4 6 8 10 12 14 16 18

  • bkg. [counts/keV/kg/y]
  • 0.01 with 90% enr.

0.04 with 90% enr. 0.01 0.04

CUORE + Čerenkov + enrichment

18

γ bkg. (MC)= 0.001

slide-19
SLIDE 19

Signal/Noise of light detector

1 2 3 4 5 6 7 8

y]

26

DBD sensitivity [10

  • 68% 0

2 4 6 8 10 12 14 16 18

  • bkg. [counts/keV/kg/y]
  • 0.01 with 90% enr.

0.04 with 90% enr. 0.01 0.04

CUORE + Čerenkov + enrichment

18

Present: S = 105, N = 75 eV γ bkg. (MC)= 0.001

slide-20
SLIDE 20

Signal/Noise of light detector

1 2 3 4 5 6 7 8

y]

26

DBD sensitivity [10

  • 68% 0

2 4 6 8 10 12 14 16 18

  • bkg. [counts/keV/kg/y]
  • 0.01 with 90% enr.

0.04 with 90% enr. 0.01 0.04

CUORE + Čerenkov + enrichment

18

Present: S = 105, N = 75 eV Target γ bkg. (MC)= 0.001

slide-21
SLIDE 21
  • ZnSe
  • Target: build a bolometric experiment of ~ 10 kg of 82Se
  • Status: Isotope in production, crystal growth under optimization.
  • ZnMoO4
  • Target: build a bolometric experiment of ~ 10 kg of 100Mo
  • Status: MoU with IN2P3 and ITEP in consideration.
  • TeO2
  • Target: develop light detectors with S/N improved by a factor 4.
  • Status: KIDs and Neganov-Luke detectors under development.

Overview until 2015

19

slide-22
SLIDE 22
  • ZnSe
  • Target: build a bolometric experiment of ~ 10 kg of 82Se
  • Status: Isotope in production, crystal growth under optimization.
  • ZnMoO4
  • Target: build a bolometric experiment of ~ 10 kg of 100Mo
  • Status: MoU with IN2P3 and ITEP in consideration.
  • TeO2
  • Target: develop light detectors with S/N improved by a factor 4.
  • Status: KIDs and Neganov-Luke detectors under development.

Overview until 2015

19

baseline

slide-23
SLIDE 23

CUORICINO data

α’s (+ β/γ’s?)

130Te 82Se 100Mo

α’s + β/γ’s

so far:

82Se and 100Mo arrays will answer

CUORE (130Te) will measure the reduction

Ultimate background: β/γ

  • So far, we do not have a measure of the β/γ background above

2615 keV with bolometric arrays à la CUORICINO, and of the CUORE β/γ background at the 130Te Q-value.

20

slide-24
SLIDE 24
  • To cover the entire inverted hierarchy of neutrino masses a

bolometric experiment operated in the CUORE cryostat will require:

Crystal R&D Status ΔE (keV) Bkg. reach Enrichment cost (€/g) Zn82Se Zn100MoO4

130TeO2

(Čerenkov)

Isotope/crystals in preparation

13 likely 75

(contract) MoU to be signed

6 likely 100-130

(estimate) CUORE experience Light Detectors

5 to be proved 10-20

(estimate)

✓1 ton isotope ✓Bkg < 1 count/keV/ton/y ✓ΔE ~ 5 keV FWHM

Conclusion: which one after CUORE?

21

slide-25
SLIDE 25

Backup

slide-26
SLIDE 26
  • natTeO2 bolometers (34% 130Te),

750g each (ΔE =5 keV FWHM)

  • Past: Cuoricino
  • 62 bolometers

11 kg (130Te)×2y, Bkg: 0.16 cpy/keV/kg

  • T0ν1/2 > 2.8×1024 years (90% CL)

〈mββ〉< 300~700 meV

  • Future: Cuore (data taking in 2015)
  • Expected bkg: 0.01~0.04 cpy/keV/kg
  • Exp. T0ν1/2 > 1.6 ×1026 years

〈mββ〉< 40~94 meV

  • Present: Cuore-0, a CUORE-like tower.
  • same mass of Cuoricino, 0.05 cpy/keV/kg.

Energy [keV]

2480 2500 2520 2540 2560 2580

Rate [counts/ (1 keV)]

5 10 15 20 25 30 35 40 45 50 Best Fit 68% C.L. 90% C.L.

0νDBD

60Co γ + γ

Cuoricino

130Te CUORE

23

CUORE - @LNGS

CUORE: 988 bolometers 750 kg TeO2 200 kg 130Te

slide-27
SLIDE 27
  • The spread in the values does not influence the isotope choice.
  • Generates problems when comparing exclusions and evidences

from experiments running different isotopes.

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

M

0ν

QRPA EDF PHFB IBM-2 LSSM

76Ge 82Se 96Zr 100Mo 116Cd 124Sn 130Te 136Xe 48Ca 150Nd 128Te

NME .

24