A study on CaMoO4 crystal coupled with LAAPD 

for neutrinoless double beta decay 

Sejong UniversityJung il LEE

LEE J.I., BHANG H.C.1, CHOI J.H.1, KIM S.C.1, KIM S.K.1, KIM S.Y.1, KWAK J.W.1, LEE J.H.1, LEE H.S.1, LEE J.1, MYUNG S.S.1, YANG H.Y.1, KIM Y.D., MOON S.H., KIM H.J.2, SO J.H.2, YANG S.C.2, HWANG M.J.3, KWON Y.J.3, HANH I.H.4, PARK I.H.4, LEE M.H.5, SEO E.S.5, 

LI J.6, ZHU J.J.7, HE D.7, YUE Q.7

Sejong University,Physics.  1Seoul National University,Physics.  2Kyungpook National University,Physics.  3Yonsei University,Physics.  4Ewha Womans University,Physics.  5Univ. of Maryland.  6IHEP.  7Tsinghua University. 

• Introduction• Double Beta Decay (DBD)?• For CaMoO4 crystal & LAAPD • Results of experiment for LAAPD• CaMoO4 data result • Results

Outline

DBD(Double Beta Decay)

2+

0+

0+

0+

2-

Ge76

As76

Se76

EndpointEnergy

(2): Allowed and observed 2nd order weak process.

(0): requires massive Majorana neutrinos.

e

e

e

e

n

n n

np

p

p

p

2222 epn

에너지

Event수 20

Motivation - Why CaMoO4 Crystal ?• Mo 를 포함하는 Active detector 중 상온에서 가장 섬광효율이 높다 .

Lightoutput increases by factor 3.5 @ 150K

Mikhrin et al. NIM 486, 295(2002)

   상온에서   CsI(tl) 의  20%  light increase at lower temperature CaMoO4 may be very good crystal for DBD

Why LAAPD(Large Area Avalanche Photodiode) ?

Advanced Photonics 사의16mm 직경의 LAAPD(world largest)

•   High quantum efficiency : High quantum efficiency : 약  약   90% @ 90% @ 500nm 500nm PMTPMT 의  경우 약 의  경우 약  10-25%10-25%

Solovov(1999)5mm LAAPD

LAAPDLAAPD 는 는  -- 200200 도에서도 도에서도 작동작동 .. Significantly reduced dark current Higher gains can be achieved Noise level can be reduced

CaMoO4 + LAAPD can be excellent detector for DBD

Previous Results of LAAPD

• CsI(Tl) + 16mm LAAPD • 4.8%FWHM for 662 keV• LAAPD has better resolution    than PMT due to high Q.E.

M. Moszynski

Room temperature measurements

5.9 keV X-ray9.3% FWHM =4.0% RMS

Source

ORTEC PREAMPLIFIER 142AH

(High Voltage 용 )POWER SUPPLY(HV)

ORTEC

AMPLIFIER 571

Crystal

LAAPD

Output (Room Temperature)

Output (Low Temperature)

Experimental Setup

CaMoO4, CsI R&D Crystals

14.3x15x13.7mm14.3x15x13.7mm-Crystal bank at Pusan National University

-CsI & CamoO4 Russia Crystal   ~10x10x10mmx10x10mm

•  투명 , nonhydroscopic•  밀도  : 4.4 (CaMoO4)

CsI(Tl) 과 CaMoO4 의 상온에서의 비교

2.7%(6.3FWHM)

Light output;CaMoO4/CsI=6.3%   Mikhrin  데이터보다  CaMoO4 의  scintillation efficiency  가 낮다 . 

3 인치 PMT with 137Cs 소스 (662 keV)

CsI(Tl) CaMoO4

Charge(arb. Unit)

9.9%(23.27FWHM)

Charge(arb. Unit)

Test on CsI(Tl)+LAAPD @Room temperature

•HV ; +1750

•Source ; 137Cs

•Threshold ; 36mV

•Size ; 10*10*10mm

Compton edge

Channel number

# o

f even

ts

Back scatters

(6%FWHM)

We confirmed good resolution of CsII(Tl)+LAAPD detector at room temperature 

CaMoO4+LAAPD @LowTemp

• Decay time ~ 100 s @ -150 oC • But shaping time of AMP is limited by 10 sAnalyzed PreAmplifier Signal directly.• Source ; Cs-137• Temp ; -159.2 oC ± 0.1

P0 = amplitude, P2=decay time, P4=rising time, P5 = backgroundP6= start time

Micro sec

mV

p4

p6

p0

p2

p5

5/)(

2

/)(

2

0 4626 exp1

exp ppp

pf pptpptfit

0 의의의의의의의  3 MeV  에너지 영역에서는 약  5.3%(FWHM) 의  energy resolution이 예상된다 .

FWHM%3.5RMS%24.23043

662RMS%7.4)expected(0

keV

keV

resolutionCompton edge

•4.7%(11FWHM) Resolution with CaMoO4 crystal in low temperature(-159°C)

(11FWHM)

• 10kg 100Mo enriched(95%) CaMoO4 (~100kg natural)

• 6% FWHM @ 3MeV energyEstimated background counts in 1 year in 1 FWHM energy region•48Ca double beta decay(T1/2=4X1019  y)

• 100Mo double beta decay(T1/2=8X1018 y)

T(1/2) > 3.3X1024 year Current best limit: 5x1022 years (Ejiri)

3.5x1023 years(NEMO)

Sensitivities of CaMoO4

)2(48 Ca

)2(100 Mo

)0(100 Mo

Conclusion & Future Plan

• Studies on temperature dependencies• Studies on PbMoO4 with LAAPD• realistic resolution test with 208Tl(2.6MeV) Source

100mm

30mmCaMoO4(310g)

• Studied CaMoO4 Crystal + LAAPD detector at room temperature & low temperature.

• Obtained 4.7% RMS resolution for 662 keV, and expect  5.3% FWHM resolution for 0 Signal

Why CaMoO4 Crystal ?

Mo-100 2nuMo-100 2nu

Ca-48 2nuCa-48 2nu

Tl-208Tl-208

Bi-214Bi-214Signal (m=0.3eV)Signal (m=0.3eV)

• Light output :20% of CsI(tl)• light increase with lower temperature•Decay time :16.6+-0.1 micro sec• Pulse shape discrimination capability

Various Backgrounds and signal estimation with 20kg of CaMoO4 with 5 years data taking (GEANT4)

Future plan & Results

• Remake of Low temp installation• Test of PbMoO4 crystal• DBD experiment start (if possible)

Thank you !!!!!!!!!!!

Set up Source

Crystal

LAAPD

ORTEC PREAMPLIFIER 142AH

POWER SUPPLY(HV)

ORTEC AMPLIFIER 571

Mikhrin et al. NIM 486, 295(2002)Studies on Molybdates, CaMoO4, SrMoO4

Emission spectrum

20% of CsI(Tl) @ 300KDecay time 16 s

Lightoutput increases by factor 3.5 @ 150K

DBD(Double Beta Decay)

2+

0+

0+

0+

2-

Ge76

As76

Se76

EndpointEnergy

(2): Allowed and observed 2nd order weak process.

(0): requires massive Majorana neutrinos.

e

e

e

e

n

n n

np

p

p

p

2222 epn

According to Advanced Photonix

RbCs 3 인치 PMT data(room Temp)

3.3%Am-241(5.6MeV)

19.3%Am-241(5.6MeV)

5.4%(FWHM)Cs-137(662KeV)

5.2%Cs-137(662KeV)

Light output;CaMoO4/CsI=5.4%

Light output;CaMoO4/CsI=5.9%•Inconsistent with “Mikhrin”

Russia crystal

Pusan Univ. crystal

Channel number

# o

f even

ts

LAAPD-Room temperature data

HV ; +1750Source ; Fe-55Threshold 20mVw/o Crystal3.5eV/1e-h pair

Statistically, expected e-h pair from 5.9 keV3.5 eV/ e-h pair in Silicon5900/3.5 ~1700 e-h pair2.4% RMSNoise contribution is dominant

selectroniclaapd

lstatistica

noise

stat

noisestatmeasured

:

:2

2

222

20.3%FWHM

CsI & CamoO4 at LAAPD 1

(88KeV)

CsI crystal

CamoO4 Crystal?

•LAAPD• Room Temp•Source ; Cd-109

CsI vs CaMoO4 at LAAPD 2

CsI 10xx10xx10mm

CaMoO4 10x10x10mmx10x10mm

# o

f ee

ven

ts

# o

f ee

ven

ts

Mean;2.715

Mean;0.0509

•Light output ; 1.9%•Am-241 Source(5.6MeV)

Channel number

Channel number

• 10kg 100Mo enriched(95%) CaMoO4 (~100kg natural)6% FWHM @ 3MeV energyEstimated background counts in 1 year in 1 FWHM energy

region1. 48Ca double beta decay(4X1019  y) 32.02. 100Mo double beta decay(8X1018 y) 7.43. Background assuming Solotvina exp(0.03

/kg/keV/year) 109.2 (conservative)Total 148.7 counts/ year T(1/2) > 3.3X1024 year

Current best limit: 5x1022 years (Ejiri)3.5x1023 years(NEMO)

Sensitivities of CaMoO4

Sample 2(20x20x10mm)0.4 pe/keV14.4% FWHM expected17.3% FWHM measured.

%1.83034

662%3.17