1. Metal loaded liquid scintillator for the double beta decay
Presented by I.C.Hwang
Yonsei University

2. Double beta decay

3. Double beta decay process
(A,Z+1)
(A,Z-1)
(A,Z)
(A,Z)
(A,Z+2)
(A,Z-2)
(A,Z) -> (A,Z+2) + 2b +2n (A,Z) -> (A,Z-2) + 2b+ +2n
EC+b+ ,2EC also is possible
Excited state g
b+ -> g g (511 keV)
Ground state

5. Why high-Z loaded scintillator?
Advantage
a) Some high-Z can't be used for inorganic scintillator.
b) high-Z can be loaded to LS (>50% or more)
c) Fast timing response (few ns)
d) Low cost of LS, Large volume is possible
e) U/Th/K background for LS is low and purification is
known
f) alpha/gamma separation may be possible
Disadvantage
a) Bigger volume is necessary (C,H in LS, low density)
b) Moderate light output (~15% of NaI(Tl))

6. HV + LSC
LSC test sample
Setup
VME

7. Setup VME Gate & Delay generator Computer Dark Box Discriminator 1 8 2
Gate:200ns
Delay:250ns
Computer
Dark Box
Co60 LSC
H1161
Th:50mv
Discriminator

8. Metal-loaded LSC for DB
STD : Solvent+Solute+ Wavelength shifter
* Solvent; PseudoCumene,
Solute: PPO (4g/1liter), WLS: POPOP (30mg/liter)
Tin compound
1) Tetramethyl-tin (40%w50%) : flammable,expensive
2) Tetrabutyl-tin (19%w50%)
Zr compound
Zr4-ethylhexanoate (Zr4-EH+mineral-oil , Zr: 6%)
Nd compound
Nd2-ethylhexanoate (Nd: 12.5%)

9. Zr2EH + LSC with Co60

10. Nd2EH + LSC with Co60

11. TetraButhyl Tin + LSC with Co60

12. TetraMethyl Tin + LSC with Co60

13. Plan
Long term Stabillity Zr2EH(50%),Nd2EH(50%),TM(50%),TB(50%)
Characteristics in bigger volume
1L * 4 : two of them are St cover, the others are acrylic.
electronics 500MHz FADC to identify and reject
U238, Th 232 decay chains
Pilot experiment :Underground with Pb shielding for the long term test
If successful, we can set the 0-nu double beta decay limit for the Sn, Zr, Nd