LARGE UNDERGROUND XENON

Transcription

1 LARGE UNDERGROUND XENON Cláudio Silva (LIP Coimbra) On behalf of the LUX Collaboration IDPASC Dark Matter Workshop 17 December

2 THE LUX COLLABORATION Collaboration was formed in 2007 and fully funded by DOE and NSF in Brown University Lawrence Berkeley National Laboratory University of California - Berkeley University of California - Santa Barbara Texas A&M University University of South Dakota Case Western Reserve University Lawrence Livermore National Laboratory LIP/ Universidade de Coimbra University of California - Davis Yale University Harvard University University of Maryland South Dakota School of Mines University of Rochester

3 LUX OVERVIEW Uses well proven technology 300 kg liquid xenon (active zone) Thorough calibration with internal and external sources Water active veto covering 4π 59 cm 49 cm Ultra-low background materials 3

4 LUX DETECTOR Double phase xenon TPC Primary scintillation (S1) and electroluminescence (S2) viewed by 122 PMT s (2 inch ) Drift length - 50 cm 4

5 5

6 DISCRIMINATION IN DUAL PHASE XENON DETECTORS S2/S1γ >> S2/S1WIMP Electroluminescence-to-scintillation ratio allows discrimination between electronic and nuclear recoil events. 6

7 XENON DETECTORS Liquid Xenon detectors are scalable Xenon allows self shielding log10 (dru) Depth(cm) 10 kg It s quiet in the middle 100 kg 300 kg 1000 kg Radius (cm) dru = events/kg/day/kev 7

8 DETECTOR DESIGN Thermosyphon LN bath column Titanium Vessels Feed-throughs for cables / pipes Radiation Shield PMT holding copper plates 59 cm 49 cm Dodecagonal field cage + PTFE reflector panels Copper Counterweight 8

9 DETECTOR DESIGN 2 kv/cm drift field in liquid 5 kv/cm for extraction 59 cm Anode grid 10 kv/cm in gas 49 cm phase Cathode grid 9

10 LUX BACKGROUNDS PMT radioactivity gives the dominant background Internal backgrounds dominate over external (from cavern rock) 10

11 LUX BACKGROUNDS PMT radioactivity gives the dominant background Internal backgrounds dominate over external (from cavern rock) 10

12 LUX CALIBRATION External sources 133 Ba, 137 Cs, 22 Na, 208 Tl: ER band 241 Am/Be: NR band Internal sources (fill entire fiducial volume) 83m Kr (half-life 1.86 hours) Tritium as CH3T (β, half-life 12.3 yrs) 11

13 THE LUX DETECTOR termosyphon breakout cart conduits water tank source delivery conduit 12

14 THE WATER SHIELD Cherenkov based active shielding, with 20 PMTs Ø10 each γ suppression: x10-9 Neutron sup. (En >10 MeV ~10-3 and En <10 MeV >10-9 ) Flux Attenuation in Water (Geant4 MC) Flux Reduction Rock Neutrons (<10 MeV) Gammas!-induced Neutrons (>10 MeV) Shield Thickness (m) 13 Inverted Steel pyramid

15 THE SANFORD LAB Sanford Laboratory at Homestake (Lead, South Dakota) once an Au mine. Homestake Davis Cavern (Former Home of the Homestake Solar Neutrino Experiment) Raymond Davis (Nobelpriset i fysik 2002) 14

16 THE SANFORD LAB Laboratory 1.5 km deep (4300 m water eq.), μ flux reduced 10-7 compared to sea level) Davis Cavern, December

17 LUX SURFACE LAB LUX assembly Full-scale test of LUX Liq/gas system PMT testing DAQ testing Xenon purity 16

18 ASSEMBLING LUX 17

19 LUX IN THE SURFACE - RUN 01 April-May 2011 First LUX cool down - test of cryogenic system 20 PMTs (10 top, 10 bottom) -1 atm argon exchange gas 300 Average Detector Temperature [K] /15 00:00 05/22 00:00 05/29 00:00 06/05 00:00 Date 18

20 LUX IN THE SURFACE - RUN 02 Started on September 2011 Full arrays of PMTs (61 top, 61 bottom) and 350 kg of liquid xenon 19

21 LUX EXPECTED BACKGROUNDS 100 days acquisition, 100 kg fiducial mass γ background ER background: 23 events }ER NR band mean NR band -3σ }NR NR background: <0.1 events 20

22 LUX EXPECTED SIGNAL 100 days acquisition, 100 kg fiducial mass γ background WIMPs For: mwimp = 100 GeV/c 2 and σwimp = 3.5x10-45 cm 2 21

23 LUX EXPECTED SIGNAL 100 days acquisition, 25 kg fiducial mass 1 single background event 22

24 LUX EXPECTED SIGNAL 300 days acquisition, 25 kg fiducial mass ER NR Longer exposure, signal becomes better defined. 23

25 LUX DARK MATTER SENSITIVITY Edelweiss II - first result Zeplin III (2009) CDMS CDMS Zeplin III, expected (2011) LUX 300 days (expected) 24

26 LUX-ZEPLIN (LZ) PROGRAM LZ is joint collaboration of LUX and ZEPLIN LZS:1500 kg, designed to be accommodated in the current LUX infrastructure σχ = 2x10-47 cm 2 in 2 years LZD: 20 ton in a deeper site (2500 m) σχ = cm2 in 3 years LZ20 20 tonnes (baseline design) ZEPLIN-III 12 kg LUX 350 kg 25

27 LUX-ZEPLIN (LZ) PROGRAM LUX 100kg X 30 days LZS 1200kg X 500 days LZD 13500kg X 1000 days 26

28 SUMMARY LUX experiment uses well proven dual-phase TPC technique Surface commissioning is in progress. Underground deployment in early spring 2012 Expected sensitivity of σχ = 7x10-46 cm 2 Plan to run for 300 days LUX has a strong potential for WIMP discovery 27

29 THANKS! 28

30 LZ PROGRAM LZ, ULTIMATE SEARCH? Electron Recoil signal limited by p-p solar neutrinos Subdominant with current background rejection Nuclear Recoil background: coherent neutrino scattering 8 B solar neutrinos Atmospheric neutrinos Diffuse cosmic supernova background LZ-D reaches this fundamental limit for direct WIMP searches LZ-D also sensitive to ββ0ν decay in natural xenon up to lifetimes of ~ years! 29

31 INTERNAL SOURCES - KRYPTON 83m Kr 30

32 INTERNAL SOURCES -TRITIUM Tritiated methane (CH3T) removal experiment Gaseous proportional tube counter (Univ. of Maryland) Xe proportional tube for CH 3 T counting Xe purifier CH 3 T storage bottle > 99.9% of CH3T removed from proportional tube in one pass through the purifier. 31

33 NR SCINTILLATION EFFICIENCY A. Manzur et al., arxiv: v4 and references therein 32

34 LUX TIMETABLE 2007/ LUX 0.1 run test in Case Western Reserve University (Cleveland, Ohio) 12/ LIP Coimbra participation started 5/ Surface Run 01: Argon gas run test 9/2011- Surface Run 02: Liquid xenon surface run test 3/2011- Underground deployment. 33