Background suppression in large mass TeO2 bolometers with

Neganov-Luke amplified light detectors

Luca PattavinaINFN-Laboratori Nazionali del Gran Sasso

luca.pattavina@lngs.infn.it

L. Pattavina 1, N. Casali 2, L. Dumoulin 3, A Giuliani 3, M Mancuso 3, P de Marcillac 3, S Marnieros 3, S.S. Nagorny 6, C. Nones 4, E Olivieri 3, L. Pagnanini 6, S. Pirro 1, D. Poda 3, C. Rusconi 5, K. Schaeffner 1, M. Tenconi 3.

1 INFN – Laboratori Nazionali del Gran Sasso, I-67100 Assergi (AQ), Italy 2 INFN – Sezione di Roma I, I-00185 Roma, Italy 3 CSNSM, Centre de Sciences Nucléaires et de Sciences de la Matière, CNRS/IN2P3, Université Paris-Sud, 91405 Orsay, France 4 CEA, Centre d’Etudes Saclay, IRFU, 91191 Gif-Sur-Yvette Cedex, France 5 INFN – Sezione di Milano-Bicocca I, I-20126 Milano, Italy 6 Gran Sasso Science Institute, I-67100 L’Aquila, Italy

1

OUTLINE• Double-beta decay investigation with TeO2 macro-

bolometers

• TeO2 Cherenkov light emission

• Neganov-Luke amplification in Light Detectors

• Prototype detector

• Conclusions

2

0vββ methods & signature- 0vββ can unveil most of neutrino properties (mass, Nature, hierarchy)

- It occurs only in few natural isotopes: 76Ge, 82Se, 100Mo, 130Te, 136Xe (and not many others).

- Signature: peak at the sum-energy (Q) of the two electrons (2-4 MeV).

Calculated energy spectrum

33

0vββ investigation with TeO2- Particle energy converted to temperature variations

Absorber operated @ cryogenic temperature (~10mK)

- Bolometer features:

high energy resolution O(1/1000)

high detection efficiency (source = detector)

scalable to large masses

fully sensitive device no particle ID in TeO2 bolometers dominant background:

α decays on the detector surfaces

Sens

itive

th

erm

omet

ers:

NTD

ther

mis

tor

�T

=E/C

⇠10

0µK E=2.6 MeV

ΔE=5 keV

4

Energy [keV]2600 2800 3000 3200 3400 3600 3800

Even

t Rat

e [c

ount

s/keV

/kg/

y]

-210

-110

1

10

Cuoricino

CUORE-0

DBD ROI

CUORE-0 background energy spectrum

CUORE coll. Eur. Phys. J. C 74, 2956 (2014)

-> See Lucia Canonica T4.4

-> See Carlo Ligi T4.5

4

Background suppression in TeO2T. Tabarelli in Eur. Phys. J. C (2010) 65: 359–361 proposed for the first time: background

ID in TeO2 calorimeter using Cherenkov light emission from beta rays.

Cherenkov thresholdEe- > 50 keV

Eα > 400 MeV

@ 130Te Qββ (2.5 MeV)

~220 Cherenkov photons (300-900 nm) ➞ 600 eV

No Cherenkov photons from natural radioactivity

A positive tagging of 0vββ is possible by means of a proper Light Detector

facing a TeO2 calorimeter

Radio-pureLarge Area

Low thresholdOperated at low T

➞ low bkg investigation➞ high efficiency➞ large signal ➞ …

Bolometric Light Detector5

First detection of light from TeO2

25 g TeO2 “Scintillation” light : 125 eV @ 2.6 MeV

in 2003

6

State of the art for large TeO2TeO2mass

Reflector/Diffusor

Light Detector

β/γ light in eV @ 2615 keV

Baselineσ [eV]

DiscriminationPower @ ROI ref.

750 g PTFEGe +

NTD105 74 1.5 Eur.Phys.J. C75

(2015) 1, 12

750 g 3M VM2002Ge +

NTD101 72 1.5 Eur.Phys.J. C75

(2015) 1, 12

285 g 3M VM2002SOS

+ W-TES

129 23 3.7 Astropart.Phys. 69 (2015) 30-36

117 g 3M VM2002Ge +

NTD195 97 1.4 Astropart. Phys. 35

(2012) 558

Expected light signal from a 750 g TeO2 ~200 eV

Observed light signal O(100 eV) ➞ low noise LD are needed➞ large area detector

Light trapping inside the crystallarge mass crystals = higher sensitivity

smaller crystal = more light A compromise is needed

7

NTD-based LD with Neganov-Luke effect:

Photons:- Electron-hole pairs- Drift by applied voltage- Additional phonons- Amplification

Total energy deposited in the absorber with applied field V:

ETOT =E

✏eV + E

Drifting charges produce phonons

Neganov-Luke effect

Ec Voltage

Amplification factor:

G = 1 +eV

✏

B. Neganov, V. Trofimov. 1985. Otkryt. Izobret. 146, 215

P.N. Luke. 1988. J. Appl. Phys. 64, 6858

8

Light detector produced at CSNSM (France)

Neganov-Luke effect on LD

0.00#

50.00#

100.00#

150.00#

200.00#

250.00#

300.00#

350.00#

0# 5000# 10000# 15000# 20000# 25000# 30000# 35000#

RMS$filtered$no

ise$[eV]$

Vluke$[mV]$

Baseline Noise

0.00#

1.00#

2.00#

3.00#

4.00#

5.00#

6.00#

0# 5000# 10000# 15000# 20000# 25000# 30000# 35000#

Norm.&A

mplifica.o

n&

Vluke[mV]&

Amplification

Entries 1310

Mean 5.99

RMS 0.6093

Integral 1310

Energy [eV]4 4.5 5 5.5 6 6.5 7 7.5 8

coun

ts /

0.1

0

20

40

60

80

100

Entries 1310

Mean 5.99

RMS 0.6093

Integral 1310

Kα

Kβ

Baseline energy resolution @ 0 keVσ = 185 eV

Signal amplitudeA = 1 uV/keV

55FeVgrid=0V

• HP-Ge wafer (44 mm X 180 um)• Al electrodes (EDELWEISS-like)• IR LED faced to LD• 55Fe X-ray calib. source• Thermal sensor: Ge-NTD

9

Experimental set-up

TeO2 5x5x5 cm3

pictures

LD + TeO2

10

GeLuke baseline σ: 0.48 mV Light @ 2615 keV: 0.24 mV

Vgrid OFF

Gain = 1

preliminary

11 S/N = 0.5

β/𝛾 events

α events

GeLuke baseline σ: 0.56 mV Light @ 2615 keV: 1.01 mV

Ligh

t am

plitu

de [a

.u.]

Vgrid ON : 30 V

preliminary

12

Gain = 4.2S/N = 1.8

β/𝛾 events

α events

GeLuke baseline σ: 0.63 mV Light @ 2615 keV: 1.64 mV

Ligh

t am

plitu

de [a

.u.]

Vgrid ON : 50 V

preliminary

13

Gain = 6.8S/N = 2.6

β/𝛾 events

α events

GeLuke baseline σ: 0.65 mV Light @ 2615 keV: 2.33 mV

Ligh

t am

plitu

de [a

.u.]

Vgrid ON : 90 V

preliminary

14

Gain = 9.7S/N = 3.6

β/𝛾 events

α events

GeLuke baseline σ: 0.65 mV Light @ 2615 keV: 2.33 mV

Ligh

t am

plitu

de [a

.u.]

Vgrid ON : 90 V

Gain = 9.7Baseline energy resolution

@ 0 V σ = 185 eV@ 90 V σ = 19 eV

preliminary

15

β/𝛾 events

α events

α β/γpreliminary

Light Yield [a.u.]

Vgrid ON : 90 V

Discrimination power: 2.7 σ

preliminary

16

• TeO2 bolometers proved to be suitable detectors for ββ investigation

• Cherenkov light detection is an excellent technique for background suppression in TeO2 crystals

• NTD-based Neganov-Luke amplified LD is a simple but a highly effective technology for particle identification

• low energy threshold -> NL-amplification

• robust, stable and reproducible performances -> NTD thermistors

• There is still room for improvements: LD coating for increasing light collection efficiency, lower baseline energy, crystal shape optimization.

Conclusions

17

Amplification characterizationEntries 1310

Mean 5.99

RMS 0.6093

Integral 1310

Energy [eV]4 4.5 5 5.5 6 6.5 7 7.5 8

coun

ts /

0.1

0

20

40

60

80

100

Entries 1310

Mean 5.99

RMS 0.6093

Integral 1310Kα

Kβ

Vgrid = 0 V Vgrid = 30 V Vgrid = 90 V

Whe

re is

the

55Fe

? Po

sitio

n de

pend

ence

in

tera

ctio

ns in

the

dete

ctor

RMS baseline noise: 0.65 [mV]LED Amplitude: 430.20 [mV]

RMS baseline noise: 0.48 [mV]LED Amplitude: 68.02 [mV]

RMS baseline noise: 0.56 [mV]LED Amplitude: 350.10 [mV]

LED Vgrid = 30 V

LED Vgrid = 90 V

LED

Vgrid = 0 V

55Fe

LED

19

20

5000

*

21