A study on CaMoO4 crystal coupled with LAAPD for neutrinoless double beta decay Sejong University Jung 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) Endpoint Energy  (2 ): Allowed and observed 2 nd order weak process.  (0 ): requires massive Majorana neutrinos. 에너지 Event 수

Motivation - Why CaMoO 4 Crystal ? Mo 를 포함하는 Active detector 중 상온에서 가장 섬광효율이 높다. Lightoutput increases by factor 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 사의 16mm 직경의 LAAPD (world largest)

High quantum efficiency : 약 500nm High quantum efficiency : 약 500nm PMT 의 경우 약 10-25% PMT 의 경우 약 10-25% Solovov(1999) 5mm LAAPD LAAPD 는 -200 도에서도 작동. 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-ray 9.3% 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

CaMoO 4, CsI R&D Crystals 14.3x15x13.7mm -Crystal bank at Pusan National University -CsI & CamoO4 Russia Crystal x10x10mm ~10x10x10mm 투명, nonhydroscopic 밀도 : 4.4 (CaMoO 4 )

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 137 Cs 소스 (662 keV) CsI(Tl)CaMoO 4 Charge(arb. Unit) 9.9%(23.27FWHM) Charge(arb. Unit)

Test on temperature HV ; Source ; 137 Cs Threshold ; 36mV Size ; 10*10*10mm Compton edge Channel number # of events Back scatters (6%FWHM) We confirmed good resolution of CsII(Tl)+LAAPD detector at room temperature

CaMoO 4 Decay time ~ 100  -150 o C But shaping time of AMP is limited by 10  s  Analyzed PreAmplifier Signal directly. Source ; Cs-137 Temp ; o C ± 0.1 P 0 = amplitude, P 2 =decay time, P 4 =rising time, P 5 = background P 6 = start time Micro sec mV p4p4 p6p6 p0p0 p2p2 p5p5

0  의  시그널이  있는 3 MeV 에너지 영역에서는 약 5.3%(FWHM) 의 energy resolution 이 예상된다. resolution Compton edge 4.7%(11FWHM) Resolution with CaMoO4 crystal in low temperature(-159°C) (11FWHM)

10kg 100 Mo enriched(95%) CaMoO 4 (~100kg natural) 6% 3MeV energy Estimated background counts in 1 year in 1 FWHM energy region 48 Ca double beta decay(T 1/2 =4X10 19 y) 100 Mo double beta decay(T 1/2 =8X10 18 y)  T(1/2) > 3.3X10 24 year Current best limit: 5x10 22 years (Ejiri) 3.5x10 23 years(NEMO) Sensitivities of CaMoO 4

Conclusion & Future Plan Studies on temperature dependencies Studies on PbMoO4 with LAAPD realistic resolution test with 208 Tl(2.6MeV) Source 100mm 30mm CaMoO 4 (310g) Studied CaMoO 4 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 2nu Ca-48 2nu Tl-208 Bi-214 Signal (m=0.3eV) Light output :20% of CsI(tl) light increase with lower temperature Decay time : 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 Crysta l LA AP D ORTEC PREAMPLIFIER 142AH POWER SUPPLY(HV) ORTEC AMPLIFIER 571

Mikhrin et al. NIM 486, 295(2002) Studies on Molybdates, CaMoO 4, SrMoO 4 Emission spectrum 20% of 300K Decay time 16  s Lightoutput increases by factor 150K

DBD(Double Beta Decay) Endpoint Energy  (2 ): Allowed and observed 2 nd order weak process.  (0 ): requires massive Majorana neutrinos.

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 # of events

LAAPD-Room temperature data HV ; Source ; Fe-55 Threshold 20mV w/o Crystal 3.5eV/1e-h pair Statistically, expected e-h pair from 5.9 keV 3.5 eV/ e-h pair in Silicon  5900/3.5 ~1700 e-h pair  2.4% RMS  Noise contribution is dominant 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 xx CsI 10x10x10mm x10x10mm CaMoO4 10x10x10mm e # of e vents Mean;2.715 Mean; Light output ; 1.9% Am-241 Source(5.6MeV) Channel number

10kg 100 Mo enriched(95%) CaMoO 4 (~100kg natural) 6% 3MeV energy Estimated background counts in 1 year in 1 FWHM energy region 1. 48Ca double beta decay(4X10 19 y)  Mo double beta decay(8X10 18 y)  Background assuming Solotvina exp(0.03 /kg/keV/year)  (conservative) Total  counts/ year  T(1/2) > 3.3X10 24 year Current best limit: 5x10 22 years (Ejiri) 3.5x10 23 years(NEMO) Sensitivities of CaMoO 4

Sample 2(20x20x10mm) 0.4 pe/keV 14.4% FWHM expected 17.3% FWHM measured.