Tin loaded liquid scintillator for the double beta decay experiment Presented by H.J.Kim, KIMS Yonsei Univ, 10/23/2002 Workshop on Underground and Astropparticle Physics Contents 1) Why high-Z loaded liquid scintillator? 2) Spin Dependent WIMP Search with nuclear excitation 3) Double beta decay with Tin 4) R&D status and plan for the Tin loaded LSC 5) Summary and Prospect
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Tin loaded liquid scintillator for the double beta decay experiment
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Tin loaded liquid scintillatorfor the double beta decay experiment
Presented by H.J.Kim, KIMS Yonsei Univ, 10/23/2002
Workshop on Underground and Astropparticle Physics
excitation3) Double beta decay with Tin4) R&D status and plan for the Tin loaded LSC5) Summary and Prospect
Why high-Z loaded scintillator? Advantage a) Some high-Z can't be used for the good
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 reduction for LS is low and purification is known Disadvantage a) Bigger volume is necessary (C,H in LS, low
density) b) Moderate light output (~15% of NaI(Tl)) Available Technology : B, Li( 10%),Gd(1%), Pb(5%),Sn(10%) <- Commercial Yb,In(LENS, 10%) loading
High-Z loaded LS physics Spin dependent Inelastic WIMP search * => Only theoreticl ideas. Solar neutrino detection
Purpose: Observation of 2nu at Sn-124 and setting most stringint limit on 0nu Sn-122,124 2nu,0nu DB. If we are lucky, we may be discover 0nu double beta decay.
It is important to study many DB source since theoretical prediction is diffcult in calculation
Sn 2-nu DB is not observed and 0-nu DB limit is very poor.
Theoretical predcition of 2-nu and 0-nu life time is as good as others.
Sn can be obtained with pure material : 99.999% 10% Sn LSC loading technology is available.
Sn DB limit Sn-122 -> Cd-122 : EC + beta+(0nu), Q=1922keV Sn-122 -> Te-122 : 2 0nu beta , Q=
366.2keV J.Fremlin and M.C.Walters, Proc. Phys. Soc. A65,
911 (1952) : 0nu limits > 6x1013
Sn-124 -> Te-124 : Q=2287 keV 0nu (>2.4x1017), 2nu (>1.0x1017) : J.A. Mccarthy, Phys.Rev. 90(1953) 853 Cloud chamber, 2.2g(95% enriched) Sn-124 Sn-124 -> Te-124 excited state transition limit Eric B.Norman, D.Meekhof, Phys. Lett.
195,126(1987) 110cm3 HPGe, LBL with shield, Sn 647g, 666 hour
data 2+(603)>2.4x1018, 2+(1325)>2x1018,
0+(1656)>2.2x1018
DB decay diagram of Nb,Zr,Cd and Sn
Limit of Sn 0nu and 2nu DB
Using Tin loaded LSC
Sn-LSC and characteristics * Tin loading : How much? * Light output * Attenuation length * Stability * n, gamma response Background * Sn background
HPGe measuremnet of TBSN (RND), TBSN (SR) and SnCl4 (RND)
TBSN test with 100% HPGe detector at CPL : 1.0 liter
1 week data taking. TBSN results : No extra peak compare with
background, U,Th,K peaks are consistent with the background within statistical errors. Tl-208 (2600keV peak) ; Cris. Crystal : 0.42mBq, TBSN(RND) 0.45mBq, TBSN(SR) : 0.44mBq. (about 10% statistal errors for measurements)
Sn-124, Sn-122 0,2nu DB limit * World best limit on Sn124 (E.Norman PLB 195,1987) 110cm3 HPGe, LBL with shield, Sn 647g, 666 hours About 1500events/keV at 603 keV energy Test of TBSN for a week at CPL , Preliminary results 450cm3 HPGe, 140 hours , 1.0liter TBSN : 400g of Sn About 15events/keV at 603 keV energy, full peak efficiency = 2-6%
* Preliminary Sn-124 0,2nu DB limit(68% CL) 2+ (603keV) 3.8x10^18 year (4.0x10^19 year) 0+ (1156) 1.1x10^19 year ( 2nu theory :
2.7x10^21) 0+ (1326) 1.3x10^19 year (2.2x10^18 year)* Sn-122 EC+beta+ decay ; 1.5x10^18 year
( 6.1x10^13)
Geant4 simulation for HPGe efficiency
Sn-124 DB excited level transition
Sn-112 EC+beta+ excited level
Summary * high-Z loaded LS can be good candidate for the underground experiment. * There are many physics opportunity with high-Z loaded LS, any new ideas? * Tin loaded LSC can be used for the double beta experiment. (up to 40% Sn loading) * Already we achieved world the best sensitivity
for Sn-124, Sn-122 excited level decay and hope to find 2nu double beta as well as 0nu double
beta decay mode. * We need theoreticl help on DB prediction and other physics ideas.
Plan * High-Z loaded LS study more : Gd, Zn ....
PLAN ( If funding and manpower is allowed) * Coincidence experiment with Tin loaded LSC(1 liter)
+ HPGe : Almost background free and will improve sensitivity one or two order => This winter * 30-50 liter of Tin loaded LSC in prototype shielding at CPL. Sensitivity to observe 2nu DB mode. => Next summer * 1-10 ton of Tin loaded LSC or enrichment : This will allow us to compete with world next generation DB experiment ! => Future underground experiment
0 nu double beta decay
Gamma level diagram of Te-124
TBSN with HPGe detector
Limit of Sn
SD with Sn-119 * Advantage a) 24keV excitation + 20ns decay time b)100ns window; 107 random bg reduction -> almost background free
* Disadvantage a) Detection of Sn recoil energy with
quanching b) natural abundance 8.6% (enrichment?)
* Study needed a) Detail study of rate estimation with
threshold b) Recoiled Sn quanching in LSC c) Background study