1. 1SNOLAB 21 August 2006 ZEPLIN A Direct Dark Matter Search Programme using Liquid Xenon CCLRC – Rutherford Appleton Laboratory, UK Edinburgh University, UK Imperial College London, UK ITEP – Moscow, Russia LIP – Coimbra, Portugal Rochester University, USA SMU, USA Texas A&M University, USA UCLA, USA

2. 2SNOLAB 21 August 2006 The Programme ZEPLIN I* – completed/published ZEPLIN II* – taking quality dark data ZEPLIN III – ready for immediate deployment The future – clear route to tonne scale through international collaboration Technical progress Report – ZEPLIN II/III – Tim Sumner Technical progress Report – ZEPLIN IVby4 – Hanguo Wang Infrastructure & Strategy Schedule * Collaboration on these projects includes Sheffield University, UK

3. 3SNOLAB 21 August 2006 World Status

4. 4SNOLAB 21 August 2006 World Status tonne scale target ZII, ZIII

5. 5SNOLAB 21 August 2006 Two-Phase Xenon Principles

6. 6SNOLAB 21 August 2006 ZEPLIN II Continuous operation for last 100 days with 7day/week support of whole collaboration It is working well Its performance is understood It has collected quality dark matter data …some examples

7. 7SNOLAB 21 August 2006 ZEPLIN II Purity

8. 8SNOLAB 21 August 2006 ZEPLIN II Scatter plot

9. 9SNOLAB 21 August 2006 ZEPLIN II Position recovery (from S2)

10. 10SNOLAB 21 August 2006 ZEPLIN II Dark Matter Data 1.0 tonne.day of quality data collected 0.1 opened for unblinded analysis Version 1 data cuts defined Efficiencies evaluated  zero background in nuclear recoil band (to be confirmed)  1.35x10 -6 pb  1.35x10 -7 pb* in current data set  Publication intended for IDM2006 Version 2 cuts + clean  lower energy + larger fiducial volume (lower background/better position recovery) April 07  3 times current exposure * Assumes 0 bg – data not opened yet Preliminary

11. 11SNOLAB 21 August 2006 ZEPLIN II ZEPLIN III

12. 12SNOLAB 21 August 2006 ZEPLIN III Features 8kg fiducial mass High QE PMTs in liquid for excellent light collection 3.5 cm drift depth 0.5 cm electrode-less electroluminescent gap for improved discrimination reverse field region 31 small PMTs for fine position sensitivity open plan – no surfaces - reduced feedback Copper construction

13. 13SNOLAB 21 August 2006 ZEPLIN III Status Built and tested Performs as designed Journal papers –Simulation – Araujo et al. (2006) Astropart. Phys. In press –Instrument – Akimov et al. (2006) Astropart. Phys. In revision Vital experience and momentum gained from ZEPLIN II Ready for immediate deployment DM2006 - February 2006

14. 14SNOLAB 21 August 2006

15. 15SNOLAB 21 August 2006 Commissioning Tests Thermal design verified – 1litre/hour LN boil off! All PMTs operational – spe established – gains equalised Xenon transferred several times Extended runs of up to 8 weeks Am241 spectra obtained with up to 16pe/keV – a world best! Dual-range 62 channel DAQ readout Data processing and analysis system developed HV established Full-depth two-phase signal recovery Bulk light yield established Neutron calibration done

16. 16SNOLAB 21 August 2006 5 pe/keV - 3.5 x ZII Bulk light collection, S1 Charge collection, S2

17. 17SNOLAB 21 August 2006 Position recovery

18. 18SNOLAB 21 August 2006 Neutron calibration ZEPLIN III ZEPLIN II

19. 19SNOLAB 21 August 2006 Araujo et al., 2006 Sensitivity prediction

20. 20SNOLAB 21 August 2006 ZEPLIN II ZEPLIN IV/MAX 0.250 ton ZEPLIN III 30kg 8kg ZEPLIN long term strategy I + =

21. 21SNOLAB 21 August 2006 Direct Scale-up Based on the ZEPLIN II/III 250kg 250kg fiducial mass Two phase xenon 50 5-inch-PMT 19 (7 eight-in) on bottom 31 on top 30-cm total drift length Light yield ~ 4pe/keV 45kV @ E=1.5kV/cm Xenon Purification Forced Circulation in liquid phase (system being studied) Active liquid recovery ~R x H = 0.5 (m) x 1.0 (m) No R&D needed for this design!

22. 22SNOLAB 21 August 2006 Spatial separation of double scatter (S2) background events in drift direction Self Shielding Fiducial Limit µs

23. 23SNOLAB 21 August 2006 “Club54” 250kg 500kg fiducial mass Two phase xenon 50 5-inch-PMT 19 (7 eight-in) on bottom 31 on top 60-cm total drift length Light yield ~ 4pe/keV 90kV @ E=1.5kV/cm Xenon Purification Forced Circulation in liquid phase (system being studied) Active liquid recovery ~R x H = 0.5 (m) x 1.3 (m)

24. 24SNOLAB 21 August 2006 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

25. 25SNOLAB 21 August 2006 250kg detector

26. 26SNOLAB 21 August 2006 VI Xe Target VII Xenon Purification and Safety System for ZEPLIN IV VI, VII, are vacuum pumps Active Xenon collection system will take less space (1.4 x linear size) Xenon purification in liquid phase (less cooling power) Manual Valve Cooling Pump Getter. Safety Dump Cooling Vacuum Insulated Line C.B. C.B. Control Box Forced recirculation system

27. 27SNOLAB 21 August 2006 ZEPLIN IV/MAX layout 1, Target Detector: (250kg  ton scale) 8m x 8m x 6m (WxLxH) Central detector, Active neutron and Compton veto Lead shield, Neutron Shield. 2, Electronic & Control: 5m x 4m x 3m DAQ system, Slow control, 3, Auxiliary systems: 8m x 8m x 4m Active xenon recovery system and related pipe-works and controls 4, Total Peak Power 25kW 5, Office

28. 28SNOLAB 21 August 2006 (ZEPLIN III+IV/4) ZEPLIN IVby4 FY07Engineering Design (SNOLAB Invitation for Tech. Design) FY08Start Construction FY09Underground Installation Total US Construction $3.5M + equivalent European contribution ZEPLIN III FY07Deployment/Operation Requires shield plus veto and local collaborators FY08Upgrade/operations (PMT, depth) FY09Completion Canadian collaborators are very important to both instruments at SNOLAB tonne scale target ZII, ZIII

29. 29SNOLAB 21 August 2006 Summary ZEPLIN II is working with >1000kg-days data on tape. First limit is encouraging Routine electron lifetimes > ms Analysis cuts defined More data to come with reduced background and improved analysis  lower threshold/larger fiducial ZEPLIN III is ready to go and performs as designed. Bringing ZEPLIN III to SNOLAB provides an early science result from an existing detector and paves the way for ZEPLIN IVby4 ZEPLIN team is well versed in ‘mine’ operation/usage Combining Zeplin II&III and Xenon10, (Club54) we know the next step to 10 -10 pb (500kg)  – looking for Canadian involvements