1. Development of metal-loaded liquid scintillators
for the double beta decay experiment
연세대:황명진,권영준
서울대:곽정원,김상열,김선기,김승천,김태연,명성숙,
방형찬,이명재,이직,이현수
세종대:김영덕,이정일,임대성
경북대:김홍주
이화여대:박일흥,이은경,한인식
칭화대:J.J.Zhu

2. Double beta decay process
(A,Z)
(A,Z+1)
(A,Z+2)
(A,Z) -> (A,Z+2) + 2b + 2 n

3. Why bb decay is important?

4. 0n-DBD Present best experimental limits
1.8
<mn>* (eV)
6.0
> 1.8 ´ 1022
48Ca
Ogawa I. et al., submitted 2002
Belli et al. submitted PLB
Experiment
<
> 7 ´ 1023
136Xe
Range <mn>
T1/20n (y)
Isotope
1.0
1.9
4.8
0.38
0.35
Bernatowicz et al. 1993
Zdenko et al. 2002
Ejiri et al. 2001
Aalseth et al 2002
Klapdor-Kleingrothaus et al. 2001
1.5
Mi DBD n 2002
<
> 2.1 ´ 1023
130Te
<
> 7.7 ´ 1024
128Te
<
> 1.3 ´ 1023
116Cd
<
> 5.5 ´ 1022
100Mo
<
> 1.57 ´ 1025
> 1.9 ´ 1025
76Ge
* Staudt, Muto, Klapdor-Kleingrothaus Europh. Lett 13 (1990) 31

5. Why metal loaded liquid scintillator?
Advantage
a) high-Z can be loaded to LS (>50% or more)
b) Fast timing response (few ns)
c) Low cost of LS, Large volume is possible
d) U/Th/K background for LS is low and purification
is known
Disadvantage
a) Bigger volume is necessary (C,H in LS, low density)
b) Lower light output (~15% of NaI(Tl))

6. Tin loading study Tin compound
1) Tetramethyl-tin (40%w50%) : flammable,expensive
2) Tetrabutyl-tin (19%w50%)
LS : Solvent+Solute
* Solvent ; PC 1L
* Solute ; POP 4g
* Second-solute ; POPOP 15mg
* Others ; Nd2-ethylhexanoate, Zr2-ethylhexanoate.

7. LSC test sample
HV + LSC
Setup
VME

8. Zr2EH + LSC (50% ->Zr 3%) Nd2EH + LSC (50%->Nd 6.25%)
TetraButhyl Tin + LSC (50%->Sn 20%)
TetraMethyl Tin + LSC (50%->Sn 40%)

9. Mineral Oil shield (30cm)
Passive shielding at Y2L(700m depth)
PE shield (5cm)
Pb shield (15cm)
Mineral Oil shield (30cm)

10. Double beta decay detector
Quartz glass
Plastic
Dimension
R = 5cm
H = 15.2cm
V = 1.18L
Teflon

11. h Simulated spectra of 2b decay experiment with 100Mo (Q=3034keV)
Source º Detector
(calorimetric technique) h
+ high energy resolution
- no event topology
Simulated spectra of 2b decay
experiment with 100Mo (Q=3034keV)
Modern Physics,Volume74, 2002

12. Calibration by Fermi-Dirac distribution
TBSN20% with Co60 source
Compton edge 1.12MeV
ADC
3.46keV/ADC channel

13. 3″ PMT LED Test S.P.E (100 times home-made preamp)
ADC
4.87 ADC channel/p∙e
→ 1.61p∙e/keV

14. TBSN 20% Energy spectrum

15. 0n DB(Sn-124 Q=2287KeV)
keV
keV

16. Sensitivity T1/2 = log 2 ´ e ´ N ´ T / dS e : efficiency
N : Number of double beta nuclei
T : Data taken time with year
dS : mean value s of Gaussian fitted area
(mean value is Q-value)
→ T1/2 = 1.2x1018 year by 90% C.L (Preliminary)

17. Summary 1. 1 day -> 1 year data taking ; 102 times increasing
2. TBSN 20% -> 50% loading
; 3 times increasing
3. World limit = 2~5x1017 year by 1952

18. Plan TBSN 50% and TMSN 50% study Nd2EH and Zr2EH study
Background reduction
2n DB study
Background understanding
More exact Calibration
electronics 500MHz FADC to identify
and reject U238, Th 232 decay chains