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Yang Yang Underground Lab in Korea (Y2L)

Yang Yang Underground Lab in Korea (Y2L). Li Jin IHEP/ Tsinghua Beijing , China. OCPA 2008 , HongKong. Outline. Yang Yang Underground Lab Detector for dark matter search Physics results Other issues in Y2L Summary.

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Yang Yang Underground Lab in Korea (Y2L)

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  1. Yang Yang Underground Lab in Korea(Y2L) Li Jin IHEP/ Tsinghua Beijing , China OCPA 2008 , HongKong

  2. Outline • Yang Yang Underground Lab • Detector for dark matter search • Physics results • Other issues in Y2L • Summary

  3. KIMS CollaborationKorea Invisible Mass Search collaboration H.C.Bhang, J.H.Choi, S.C.Kim, S.K.Kim, S.Y.Kim, J.W.Kwak, M.J.Lee H.S.Lee, S.E.Lee, J. Lee, S.S.Myung, H.Y.Yang Seoul National University Y.D.Kim, J.I. Lee, U.G.Kang Sejong University H.J.Kim Kyungpook National University M.J.Hwang, Y.J.Kwon Yonsei University I.S.Hahn, I.H.Park Ewha Woman's University M.H.Lee, E.S.Seo Univ. of Maryland J.Li Institute of High Energy Physics J.J.Zhu, D. He, Q.Yue, X. Lee Tsinghua University (TEXONO : close relationship )

  4. （襄阳） The Korea Invisible Mass Search (KIMS) experiment is located at the Yangyang Underground Laboratory (Y2L) at a depth of 700 m under an earth overburden in South Korea.

  5. The space of Y2L provided by the YangYang Pumped Storage Power Plant , Access to the lab by car2Km tunnel from gate, clean room with an air conditioning system for a constant temperature and low humidity.

  6. Radiation in the lab

  7. Diagram of detector& shielding Active Detector CSI Cs(Tl) Crystal Detector MUD NMD Neutron Monitor Detector PE shield (5cm) Pb shield (15cm) MUD Muon Detector - LS 5% Copper shield (10cm) CSI Passive shield NMD Copper : 10 cm PE : 5 cm Lead : 15 cm Mineral Oil : 30 cm Mineral Oil shield (30cm)

  8. Y2 Underground lab PE 5cm LS30cm 宇宙线Veto 中子屏蔽体 屏蔽外部等 屏蔽外部材料的本底 OFHC Cu 10cm : 3t Pb 15cm : 30t

  9. ~ 90 cm CsI(Tl) Crystal Array ~90 cm 8cm x 8cm x 30cm 11x11 =121 crystals 1.05 t 30 cm

  10. Why CsI(Tl) Crystal ? Advantage High light yield ~60,000/MeV Pulse shape discrimination Easy fabrication and handling High mass number(both Cs and I) Relatively easy to get large mass with an affordable cost CsI(Tl) NaI(Tl) Photons/MeV ~60,000 ~40,000 Density(g/cm34.53 3.67 Decay Time(ns) ~1050 ~230 Peak emission(nm) 550 415 Hygroscopicity slight strong Disadvantages Emission spectra does not match with normal bi-alkali PMT =>Effectively reduce light yield Inner radioactivity Cs137, Cs134 , Rb87

  11. 内部放射性 137Cs : t1/2= 30.07 year (Artificial) b decay to 137Ba* (Q = 1175.6 keV)  2 min life time, emitting 661.6 keV gamma Hard to reject, serious background at low energy 134Cs : t1/2 = 2.065 year : Artificial+ 133Cs(n,) b to 134Ba* (Q=2058.7 keV)  immediate  emission Can be rejected easily : not a serious problem 87Rb : t1/2 = 4.75 x 1010 year (27.8% natural abundance) b Beta deacy to 87Sr (Q=282.3 keV)  no  emission Hard to reject => potentially a serious problem => reduction technique in material is known

  12. Backgrounds of CsI(Tl) crystal

  13. We investigated the contamination process and the reduction methodof 137Cs. By using purified water, succeeded in reducing the 137Cs in the final powder and the crystal. The reduction technique of Rb, a repeated recrystallization process, has been widely known

  14. Best available Crystal at Market Powder Selection Cs137 Reduction Using Pure water Rb87 Reduction by Re-crystallization

  15. CsI(Tl) Crystal Detector CsI(Tl) Crystal Size 8*8* 30 cm3 Weight 8.7 kg 137Cs reduction using purified water 87Rb reduction by recrystalization 3” PMT - 9269QA Quartz window RbCs photocathode CsI crystal detector module

  16. Electronics MUD CSI NMD • PREAMPLIFIER • FOR CSI • 2 CHANNELS / BOARD • x10 FOR DIGITIZER • x100 FOR DISCRIMINATOR • PSEUDO CHARGE SESITIVE • OUTPUT FOR PEAK SENSING • ADC • - 200MHz BANDWIDTH • ANALOG SUM • - FOR MUD • 3 IN - BNC • 2 OUT- BNC,REMO • 2 CHANNELS / BOARD • SEPARATE INPUT GAIN & OFFSET ADJUSTMENT • SUM OUT GAIN ADJUSTMENT • 500MS/s DIGITIZER • 2 CHANNELS / BOARD • 32us RECORDED/EVENT • 16us DT / EVENT • DOUBLE BUFFERER SRAMs (4Mbit/ CH) • TRIGGER LOGIC IMPLEMENTED • VME CONTROLLER • USB2 INTERFACE • OPTIONAL HD

  17. Typical low energy r signal from one PMT obtained by Compton event from Cs137 source

  18. ~ 90 cm 探测器 总体构造 8cm x 8cm x 30cm 11x11 =121 crytals 1.05 t ~90 cm 2005 24kg 2007 100kg 2009 30 cm

  19. Exclusion plot for the SD interaction of pure proton coupling (R) & pure neutron coupling (L) at the 90% confidence level .

  20. Exclusion plot for the SI interaction at the 90% confidence level . Crystals used in the analysis and amount of data Crystal Mass (kg) Data (kg . days) S0501A 8.7 1147 S0501B 8.7 1030 B0510A 8.7 616 B0510B 8.7 616 Total 34.8 3409 Published in PRL 99 091301(2007)

  21. WIMP search using ULEGe detector

  22. Summary • Y2L has been constructed for dark matter search ,double beta decay and ….in Korea • Low radiation background CsI(Tl) detector has built with large mass • The physics result obtained and new result will coming using larger data sample.

  23. Thanks

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