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Development of metal-loaded liquid scintillators for the double beta decay experiment

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. ( A,Z+1). ( A,Z). ( A,Z+2).

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Development of metal-loaded liquid scintillators for the double beta decay experiment

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

  3. Why bb decay is important?

  4. 0n-DBDPresent best experimental limits * Staudt, Muto, Klapdor-Kleingrothaus Europh. Lett 13 (1990) 31 Experiment Isotope T1/20n (y) <mn>* (eV) Range <mn> 6.0 48Ca > 1.8 ´ 1022 Ogawa I. et al., submitted 2002 76Ge > 1.9 ´ 1025 0.35 < 0.3 - 2.5 Klapdor-Kleingrothaus et al. 2001 > 1.57 ´ 1025 0.38 < 0.3 - 2.5 Aalseth et al 2002 4.8 < 1.4 - 256 100Mo > 5.5 ´ 1022 Ejiri et al. 2001 1.9 < 1.8 - 6.2 116Cd > 1.3 ´ 1023 Zdenko et al. 2002 128Te > 7.7 ´ 1024 1.0 < 1.0 - 4.4 Bernatowicz et al. 1993 130Te > 2.1 ´ 1023 1.5 < 0.9 - 2.1 Mi DBD n 2002 136Xe > 7 ´ 1023 1.8 < 1.4 - 4.1 Belli et al. submitted PLB

  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) Lowerlight 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. 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. e- h e- SourceºDetector (calorimetric technique) +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 + 1.64s 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

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