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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 경북대 : 김홍주 이화여대 : 박일흥 , 한인식 IHEP:J.Li 칭화대 : J.J.Zhu,D.He. ( 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 경북대:김홍주 이화여대:박일흥,한인식 IHEP:J.Li 칭화대:J.J.Zhu,D.He

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

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

  10. 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

  11. b – a coincidence candidates 238U chain • 214Bi : 3.27 MeV b-decay • g 214Po : 7.833 MeV a -decay • Lifetime of 214Po = 0.1643 ms • 100 keV Energy threshold

  12. 214Bib-decay g214Poa-decay s -> T 1/2 = 0.166ms

  13. 214Bib-spectrum 214Poa-spectrum Q=3.27MeV Q=7.833MeV Ee(keV) Ee(keV) 214Po - a decay - Quanching factor = 9.1% - 67개/day

  14. TMSN50% Energy Spectrum by CAMAC pol3 + gaus fitting Ee(keV) Ee(keV)

  15. TMSN50% Energy Spectrum by 500MHz FADC pol3 + gaus fitting Ee(keV) Ee(keV)

  16. Sensitivity T 1/2 = 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)

  17. Summary 1. TMSN50% by CAMAC -> 123 days T1/2 = 5.56x1019 year by 90% C.L 2. TMSN50% by 500MHz FADC -> 33 days T1/2 = 3.41x1019 year by 90% C.L 3. World limit = 2~5x1017 year by 1952

  18. Plan • Nd2EH and Zr2EH study • Background reduction • 2n DB study • Background understanding • More exact Calibration • U238, Th 232 decay chains study

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