ZEPLIN: A Dark Matter Direct Search Program Using Liquid Xenon

Transcription

1 ZEPLIN: A Dark Matter Direct Search Program Using Liquid Xenon Hanguo Wang, UCLA, Physics and Astronomy CSU, Nov. 18, Progress with ZEPLIN II & III, 2. ZEPLIN-IV layout and infrastructure needs, including external active shielding, and 3. Funding, schedule, and readiness for a full technical proposal.

2 Underground at Boulby Boulby Surface Infrastructure Complete Offices, Conference room, Computer network, Workshop, Laboratory space, Stores, Galley Boulby Underground Infrastructure Complete Jun 04 >1000m2 laboratory space Air conditioned, clean (15k clean room already) Environment monitoring: gas, fire, power, dust, etc. Transport infrastructure ZEPLIN II Stores, workshop, safety systems

3 ZEPLIN III PMT assembly and internals

4 Overview of the ZEPLIN Project Liquid Xenon is best suited for Dark Matter search due to its: available in large quantities with both spin odd and even isotopes high density, high atomic number compact design with high event rates scintillation and ionization yield low energy threshold & good background rejection The ZEPLIN collaboration was formed in the early 90 s. Extensive R&D on dark matter search using liquid xenon was done within ICARUS since 1990 and a number of key ideas was developed: Purification NIM A329 (1993) (electron life time 5-ms) Discrimination Principle NIM A327 (1993) 203 (Demonstrated alpha-gamma) Scintillation Efficiency NIM A449 (2000) (quenching factor measured) The Two phase detector Astropart. Phys. 12, (1999) Completed underground operation of ZEPLIN I. GJ Alner et al., Astropart. Phys. 23, Significant progress by the collaboration on ZEPLIN II and III construction and testing. ZEPLIN II detector is installed underground and expect physics result soon ZEPLIN III surface commissioning are well under way and expect completion 2005 We will learn from ZEPLIN II/III operation for issues of future ZEPLIN IV/MAX operation ZEPLIN IV/MAX ton-scale detector being studies within ZEPLIN collaboration, key issues: Low energy threshold & better background discrimination Ionization from recoil, quenching at low energies, Kr removal. Full 3-D capability of event reconstruction, PMT or charge readout The current collaboration: UCLA, TAMU, Univ. of Rochester, UKDMC, ITEP, LIP- Coimbra, and potential groups SMU Texas and Chinese Groups

5 Why Use Xenon Available in Large Quantities (35 tons annual world production) Large abundance for both s ½ ( 129 Xe~26%) and s 0 ( 132 Xe~27%) High Atomic Number (Z Xe =54, σ WIMP-Nuclei A 2 ) High Density (~ 3g/cm 3 liquid) (compact detector design) High Scintillation Light (175nm) & Ionization Yield ΔE FW Small fano factor ( F =0.04, 1 Energy Resolution = 2.35 ) E E Scintillation decay profile difference (Scint., Ion.) (PSD) Large quenching factor (observed energy/e.e.energy) Can be Highly Purified long light attenuation length (~m) long free electron life time (~5ms) Gamma & Recoil signal Discrimination Capable of Scale up to Large Volume (ton) No Long Lived Radioactive Isotopes (low background)

6 χ WIMPs χ E R 2 mnmχ 2 ΔErecoil = v (1 + cosθ ) < 100keV ( m + m ) N χ 2 dr de R 0 ER ( ) / E0r E 2 ( 2 = = e F q = 2M E ) R R E r v E 0 N R vesc = 0 R event rate per unit mass: 0.1~ events/kg/day

7 WIMP elastic nuclear recoils deposit < 100keV of energy at a rate 10-5 to 1 event/day/kg IGEX, DRIFTI, II phonons, photons and charge whose relative proportions and /or characteristics depend on de/dx particle type ZEPLIN II, III, MAX, XENON ionisation Q CDMS, EDELWEISS NAIAD, ZEPLIN I, DAMA Event-by-event particle identification requires compound information L scintillation H CRESST II, ROSEBUD phonons CRESST I World competition is intense and uses a wide range of complementary techniques

8 (A) Pulse Shape discrimination: due to decay profile difference between nuclear recoil & electron recoil (B) When E drift applied, and measure E i & E s, Very good background rejection due to (E i /E s ) M.I.P. >> (E i /E s ) H.I.P. ZEPLIN I (A) ZEPLIN II (A&B) 2ns 27ns Nuclear/Electron Recoil Excitation Xe * + Xe Ionisation Xe + E drift Xe Xe + e - ~45ns (recombination) Xe ** + Xe Xe 2 * Singlet 3ns nm WIMPs χ E R ratio Triplet 27ns nm Nuclear = 10 x electron

9 Principle Tests Setup NIM A327 (1993) Ceramic. 2.Quartz Window, 3. Stainless Steel Cathode. 4. Source. 5. Grounded Grid. 6. Anode wire frame

10 Electron lifetime and drift velocity in LXe Qc t d Qa Electron drift velocity are measured at many driftfields and temperatures Under 10V/cm drift field e-life-time > 5ms Life time measurement: Measure both injected charge Q c and collected charge Q a after drift Q a = Q c t d e τ τ = t d ln Qc ( ) Q a Lifetime measurement setup And readout electronics NIM A329 (1993)

11 (a) PMT xenon gas e - γ n-r LXe PMT e - gas liquid S2 S1 Primary (S1) Scintillation Secondary (S2) Electroluminescence

12 ZEPLIN II ZEPLIN III

13 ZEPLIN II ZEPLIN III

14 ZEPLIN II Being assembled (Not to Scale) ZEPLIN III Being assembled

15 ZEPLIN III

16

17 Summary of ZEPLIN III Operating in Surface Lab cold now for two weeks, with one xenon liquefaction so far. Thermal design validated; boil off 1 liter LN per hour and we can put xenon in and out as we wish without need to cycle chamber temperature. All 31 PMTs are working fine and right figure shows single phase PHAs from two PMTs. High precision time constant measurements down to 8keV taken with this system at zero field. Two typical PMT signals: show a 6% sigma at 60keV (peak on right) from an internal Am source. Middle peak is combination of 26keV Neptunium and escape feature from 60keV. Small feature (blue trace) is 8keV Cu flourescence line from source mount.

18 ZEPLIN II PMT Assembly 7 UV sensitive low temperature PMTs (by Electron Tubes)

19 Target Integration showing wire mesh, field shaping rings, the PTFE structure to confine liquid xenon and gas extraction device

20 Surface Tests

21 Data Acquisition PMTs Dual Out X10 AMP Discriminators out Trigger N out of 7 (31) PC Acqiris DC MHz Digitizer 2 Mbyte/channel Zep II 7(ch) * 200(µs) / 2(ns) 700kB/event Zep III 31(chx2) * 20(µs) / 1(ns) 1240kB/event

22 ZepII Liquid Test zii_51505_006.raw Scan Event # 557 ZepII RAL-Liquid zii_51505_002.raw Scan Event # Amplitude (Volts) PMT 1 PMT 2 PMT 3 PMT 4 PMT 5 PMT 6 PMT 7 Amplitude (Volts) PMT 1 PMT 2 PMT 3 PMT 4 PMT 5 PMT 6 PMT Time (Micro-Second) zii_51505_06.raw Events from liquid filled test on surface Time (Micro-Second) zii_51605_001.raw Preliminary With AmBe Source Preliminary Without AmBe Source

23 Final Integration at Boulby mine with improved HV feedthrough

24

25 Underground at Boulby Boulby Surface Infrastructure Complete Offices, Conference room, Computer network, Workshop, Laboratory space, Stores, Galley Boulby Underground Infrastructure Complete Jun 04 >1000m2 laboratory space Air conditioned, clean (15k clean room already) Environment monitoring: gas, fire, power, dust, etc. Transport infrastructure ZEPLIN II Stores, workshop, safety systems

26 ZEPLIN II system Setup Cooling and Feed-Through Stainless Steel Cast Vacuum Vessel PMT PMT Copper Cast Target Vessel The Central Detector PMT Active Veto Liquid Xenon Target Liquid Scintillator Lead Shield

27 Neutron sources Neutron production from U/Th in detector material U/Th in shielding material U/Th in rock µ spallation in detector material µ spallation in shielding material µ spallation in rock

28 Summary table of simulated neutron background rates for a 33kg liquid xenon detector at 3000mwe (Boulby Mine). Neutron source recoils/year in 5-50 kev for 30 kg Xe shielded with 30cm CH 2 & 25cm Pb with 99% muon veto no muon veto but CH 2 inner converted to 90% active neutron veto with both muon and neutron vetos Muons in rock Muons on Fe/Pb shield Muons on CH < 0 01 Muons on vac vessels 1* < 0.01 Rock U/Th 70ppbU+130ppbTh U/Th in outer Pb 0.5ppbU+0.5ppbTh U/Th in vac vessels 0.5ppbU+0.5ppbTh PMT array (7 x ETL D794Q) Total * assuming 50% of muons vetoed by detector from Bungau et al Astroparticle Physics 23 (2005) 97

29 Summary of ZEPLIN II Routine two-phase operation established underground 40kg Xenon liquefaction cycles 5 times 10 hours to fill and 6 hours to empty Calibration and preliminary data runs started System Integration Status Cooling System Stable Slow Control System operational HV System, Feedthroughs complete DAQ system and Software Tested External electron lifetime monitor incoporated Liquid level monitoring to < ¼ mm Instrument tilt/grid shape to < ¼ mm across whole surface Recirculation system installation planned for December Performance Ionization yield from Xenon nuclear recoil observed! Primary light yield as expected (~1pe/keV preliminary) >25kg.day commissioning physics run by end 2005

30 DAMA Edelweiss ZepI CDMS ZepII&III ZepII&III Upgrade ZepIV/MAX current tech. Advanced ZepIV/MAX Goal of the ZEPLIN II&III Operation Is to Search for Dark Matter at pb level And learn all issues leading to large scale design of ZEPLIN IV/MAX to probe most SUSY predicted regions

31 Direct Scale-up Based on the ZEPLIN II/III R&D 30kg One Ton Simplify Design Additional PMTs at Bottom or CsI? Double the Drift Distance ZEPLIN II/III Operation will teach us about the feasibility of direct scale-up

32 0.5-ton ZEPLIN II/III 5-ton 10-ton total 1-ton ZEPLIN IV? ZEPLIN IV?

33 ZEPLIN IV/MAX layout 1, Target Detector: (for ton scale) 8m x 8m x 6m Central detector, Active neutron and Compton veto Lead shield, Neutron Shield. 2, Electronic & Control: 5m x 4m x 4m DAQ system, Slow control, 3, Auxiliary systems: 8m x 8m x 6m Active xenon recovery system and related pipe-works and controls

34 ZEPLIN Long Term Plan (presented at SNOLAB, and SNOLAB invites ZEPLIN IV engineering design) ~3000 kg-days data Operation Operation Operation Upgrade to 1-ton ZEPLIN IV/MAX Pending (SAG)

35 ZEPLIN Collaboration Groups DB Cline, W.C. Ooi, F Sergiampietri (a), H Wang, P Smith (b), X Yang Physics and Astronomy, UCLA, (a) Pisa, (b) RAL&UCLA JT White, J Gao, J. Maxin, G. Salinas, R. Bissit, J. Miller, J. Seifert Department of Physics, Texas A&M University T Ferbel, U Schroeder (Chemistry), F Wolfs, W Skulski, J Toke Department of physics and Astronomy, Rochester University GJ Alner, C Bungau, B Camanzi, TJ Durkin,, R Luscher JD Lewin, RM Preece, NJT Smith, PF Smith Particle Physics Department, Rutherford Appleton Laboratory, Chilton, Oxon H Araujo, A Bewick, D Davidge, JV Dawson, AS Howard, WG Jones, MK Joshi, V Lebedenko, I Liubarsky, T J Sumner, J J Quenby, R Walker Blackett Laboratory, Imperial College of Science, Technology and Medicine, London MJ Carson, E Daw, J Davis, T Gamble, VA Kudryavtsev, TB Lawson, PK Lightfoot, JE McMillan, B Morgan, SM Paling, M Robinson, NJC Spooner, DR Tovey Department of Physics and Astronomy, University of Sheffield A. S. Murphy, C Ghag University of Edinburgh, Department of Nuclear Physics M. Danilov, D Akimov, A. Kovalenko, V. Stekhanov ITEP, Moscow, A. Policarpo, I. Lopes, V. Chepel LIP-Coimbra SMU, Texas Groups in CHINA

36