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UKDM Programme

UKDM Programme. Update on NaI, ZEPLIN and DRIFT. Neil Spooner, University of Sheffield. New Caverns. 50 m. More lab space than Soudan. New U/G Infrastructure 2000. £3.1M Award to University of Sheffield - Joint Infrastructure Fund grant. Collaboration with RAL Surface facilities

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UKDM Programme

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  1. UKDM Programme Update on NaI, ZEPLIN and DRIFT Neil Spooner, University of Sheffield

  2. New Caverns 50 m More lab space than Soudan New U/G Infrastructure 2000 £3.1M Award to University of Sheffield - Joint Infrastructure Fund grant Collaboration with RAL Surface facilities Workshop, offices, etc. Underground facilities New much larger clean area Upgrade of existing areas

  3. Stub 2 Stub 2a,3 ‘H’ Area 50m JIF Area Boulby U/G Facilities

  4. New JIF Underground Facility ~1500m2 new lab space Laboratories Clean rooms Workshop Mess Fibre optic/Enet Running boards 3.8m 6m Clean Bay Control Room 20m DRIFT Bay Control Room Clean Bay Experimental Halls 8m Workshop Clean Changing Transfer Transfer 14m 47m Mess 8m 20m Workshop Coms/Elecs. Store

  5. ~ 1500 m2 new space New Area Under Construction

  6. Main experimental hall will have 4-5m FLAT room DRIFT 1 site DRIFT Area Construction

  7. New Surface Laboratory

  8. Call For Proposals Institute for Underground Science Facility Management Board International Boulby Research Board Facility manager and staff Projects co-ordinator Contact me: Neil Spooner - n.spooner@sheffield.ac.uk Plenty of new lab space available

  9. existing NAIAD high rate array 50 kg NaI small array 20 kg NAIAD array ramp down UK-Saclay 20 kg existing ZEPLIN-MAX ion-scint two phase Xe 1000 kg MULTINATIONAL ZEPLIN-II ion-scint two phase Xe 30 kg ZEPLIN-I single phase PSD 4 kg ZEPLIN array under construction ZEPLIN-III Ion-scint two phase Xe high field 6 kg concept DRIFT 10 directional 10 m3 MULTINATIONAL DRIFT 1 directional 1 m3 DRIFT array under construction concept 2000 2001 2002 2003 2004+ Boulby Dark Matter Projects

  10. Imperial College of Science, Technology and Medicine:B. Ahmed, A. Bewick, D. Davidge, J. V. Dawson, A. S. Howard, I. Ivaniouchenkov, W. G. Jones, M. K. Joshi, V. Lebedenko, I. Liubarsky, T. J. Sumner, J. J. Quenby Rutherford Appleton Laboratory: G. J. Alner, E.G. Capocci, S. P. Hart, J. D. Lewin, R. Lüscher, R. M. Preece, J. W. Roberts, N. J. T. Smith, P.F. Smith University of Sheffield: T. Gamble, V. A. Kudryavtsev, T. B. Lawson, M. Carson, S. Paling, P. K. Lightfoot, J. E. McMillan, B. Morgan, M. Robinson, N. J. C. Spooner, L. Thompson, D. R. Tovey, G. Nicklin Torino: P Picchi, L Periale, G Mannocchi, C Taricco, C Castagnoli, A Curioni Saclay:G. Gerbier CERN/Padova: A Pietropaulo ITEP: D Akimov, V Lebedenko, A Danilov Coimbra: A Policarpo, M Salete Leite, R Ferreira Marques, V Chepel UCLA: D Cline, M Atac, H Wang, J K Woo, J Park Columbia: C Hailey, J Hong, E Aprile, A Castellina Temple University: C J Martoff, P Ambrozewicz, E Kaczanowicz UCSD: K Griest, G Masek, K Buckland Occidental College: D Snowden-Ifft, T Ohnuki, N Villaume, J Burwell LLNL: B Craig, M J Lehner Boulby Dark Matter Collaboration (BDMC) UKDMC People Involved in Dark Matter QMW: J. C. Barton University of Surrey:E. Morton, P. Sellin

  11. Motivation • Low-A target (Na) for WIMP masses < 200 GeV/c2 to reach 0.1/kg/d --> Complements liquid Xe high-A • Pulse shape discrimination and known technology that can be scaled up --> satisfies requirement for (i) recoil identification and (ii) diagnostic array capability • Information relevant to DAMA using the same target, NaI Boulby NAIAD Programme status and programme

  12. DE - 12-15 keV Compton NaI(Tl) Integrated Pulse-Shape neutron UKDMC NaI - PSA Schematic of early NaI detector e.g. DM46 double zone refined NaI(Tl) crystal PMT 1996 limit from DM46 spin-independent low activity silica light guides & PMT shield Example time constant distributions for new crystal DM72 showing log gauss neutron and compton fits and data.

  13. NaI Anomalous Events (1998) • Following improvement to DM46 (5 kg) - discovery of fast events in NaI Data (DE 35-40 keV) Anomaly calibration Typical fast event energy distributions in various crystals of different geometry Example t histogram for DM46 showing anomalous events

  14. UKDMC NaI + Saclay • Collaboration with Saclay to run a “DAMA” crystal at Boulby RESULT UKDMC spectrum • very similar spectrum of • fast events seen again anomalous event spectra in NaI • this despite very different manufacture and geometry Saclay (“DAMA”) spectrum

  15. DAMA PSD DAMA PSD UKDMC anomalous event spectra Limit on anomalous events from DAMA old PSD data

  16. paraffin light guide silica light guides water shielding lead/copper shielding (a) NaI Anomalous Events (1998) • Many underground and laboratory tests performed RESULT Anomaly seen in many crystals: Different manufacture, Different aspect ratio, Different history • not internal activity • too fast for neutrons • not external betas…. • most likely surface implanted outgoing alphas DE 30-40 keV alphas gammas Example t distribution for DM26 exposed to external low E alphas

  17. Outgoing Surface Alphas? • Outgoing a events • Radon implantation? • Surface contamination? • Supported by recent surface treatment results ~0.005ppb U

  18. CsI Test (DM71) anomalous events prior to surface polish known internal alphas after surface polish Identification of the events • Confirmed with CsI - easier to use unencapsulated than NaI CsI

  19. UKDMC spectrum Saclay (“DAMA”) spectrum no fast events within stat UKDMC spectrum Saclay (“DAMA”) spectrum DM74 limit on fast event spectrum t distribution for pre-polished unencapsulated crystal DM74 after 5 mns operation DM74 limit on fast event spectrum RESULT • anomalous events reduced in NaI • BUT at least 3-4 months exposure to Rn would be needed! - difficult to explain Identification of the events • Confirmed with unencapsulated NaI (DM74) anomalous event spectra in NaI Are the fast events in any way related to the DAMA result?

  20. NAIAD Design • Unencapsulated units for 5-10 kg NaI crystals built OFHC box PTFE crystal cage dry nitrogen or mineral oil crystal

  21. NAIAD Programme - H-Area • 35 kg Unencapsulated surface controlled NaI • 15 kg Encapsulated high light yield NaI • 10 kg Saclay crystal Control room H 1 H 2 H area map to JIF area crane glove box NaI unencapsulated

  22. NAIAD Installation

  23. NAIAD Preliminary Results

  24. three discrimination techniques + Xe Ionisation +Xe Nuclear/Electron Recoil (1) scintillation pulse shape + Xe 2 Excitation - +e (2) ionisation-scintillation - low field- (recombination) * ** Xe Xe + Xe +Xe (3) ionisation-scintillation - high field, low threshold - * Xe 2 175nm 175nm Triplet Singlet single phase Xe two phase Xe 3ns 27ns gas 2Xe 2Xe liquid liquid World expertise • ICARUS-UCLA • Doke group (Japan) • DAMA • Columbia • UKDMC • ITEP Boulby Xenon Programme

  25. basic ionisation-scintillation and high target mass - improve by x10 - UCLA concept demonstrate basic discrimination with PSD - set first limits A multinational programme ZEPLIN-MAX ion-scint two phase Xe 1000 kg new (5 years) ionisation-scintillation and high field - ultimate discrimination, low threshold - Boulby Xenon Programme ZEPLIN-II ion-scint two phase Xe 30 kg running ZEPLIN-I single phase PSD 4 kg ZEPLIN array under construction ZEPLIN-III Ion-scint two phase Xe high field 6 kg : Involved in programmes: UCLA, CERN/Padova, Torino, ITEP, Coimbra, Columbia, RAL, ICSTM, Sheffield

  26. Xe+ +Xe Xe2+ +e- (recombination) Xe* Xe** + Xe +Xe Xe2* 175nm 175nm Triplet Singlet 3ns 27ns 2Xe 2Xe UKDMC Xenon - ZEPLIN I

  27. ZEPLIN I Underground Boulby stub 2 laboratory xenon purification Top of ZEPLIN I veto Counts vs. time Xe temp vs. time Pb shielding room temp vs. time Stable operation demonstrated

  28. ZEPLIN Operations at Boulby

  29. ZEPLIN I Laboratory tests • PMT background events rejected by turret fiducial cuts as expected 137Cs events origin is where all 3 PMTs record identical signals turret events rejected by asymmetry cut • Compton veto (1 ton PXE) found to have ~50 keV threshold

  30. 0 500 1000 1500 2000 0 20 40 60 80 100 ZEPLIN I Laboratory tests pe/keV 2 • Light collection exceeds design spec of 1 pe/keV Z I data 1 theory 0 keV tau (ns) • Up to 50% difference in neutron and gamma time constants 50 keV 0

  31. ZEPLIN I Discrimination Gamma source  (ns) n Neutron source (ns) 10-20keV 20-30keV

  32. ZEPLIN I - Results Predictions for 1 year 85Kr < 10-17 atoms/atom

  33. ZEPLIN I Laboratory tests • Light Yield • Increases at low energy • Spatial Uniformity • 137Cs Source Data Theory

  34. ZEPLIN I - Predicted Limits

  35. ZEPLIN II (UKDMC collaboration with US and Italy) ionisation-scintillation discrimination OFHC copper plate ~30kg Lxe detector shielding, integration, readout, daq UCLA, Torino, Padova UKDMC cooling rings PTFE cone • Completion due end 2001

  36. ZEPLIN III (UKDMC collaboration with US and Russia) ionisation-scintillation - low threshold • 6 kg liquid Xe • High field (20 kV) operation for better discrimination Xe 31 two-inch photomultipliers 1kg test chamber result • Completion due end 2001

  37. 3 modules 4 sub- units One possibility shielding 80 kg target RESULT: (a) attain 0.0001/kg/d, (b) diagnostic array with complementary techniques ZEPLIN - 1 ton Concept ZEPLIN-MAX A BDMC multinational programme Options being explored: (I) single unit, (II) 4 units, (III) modular (IV) mass + low threshold units • Final design by mid 2002 • Recoil Discrimination • Construction 2004+

  38. CsI photocathodes in LXe: E.Aprile, NIMA 338 (1994), 328; NIMA 343 (1994), 121. GEM phototubes in noble gases:http://gdd.web.cern.ch/GDD/A.Buzulutskov, NIMA, 443 (2000), 164. Xe Gas GEMs CsI He Cooling Liquid Xe PTFE Reflector Field Shaping Rings CsI nucl.rec. elec.rec. PMT Removal for Scale-Up? • Sheffield test cell

  39. GEM Prototype Target High or low field operation In-house CsI photocathode production GEMs of Sheffield design from CERN

  40. GEM Rig

  41. ZEPLIN-MAX ZEPLIN-II ZEPLIN-III ZEPLIN locations at Boulby Stub 2 JIF Facility ZEPLIN-I

  42. 10-3 10-4 10-5 ZEPLIN 2002/3 10-6 ZEPLIN I/II 2003 CDMS II CRESST II 10-7 ZEPLIN II/III 2004 10-8 ZEPLIN-MAX 2006 10-9 10-10 10 100 1000 ZEPLIN-XENON Predictions NaI 1996 limit WIMP-nucleon cross-section, pb ZEPLIN predictions based on prototype tests and operation of ZEPLIN I WIMP mass GeV

  43. 6 ~30 kms-1 600 Jun. 2nd ~220 kms-1 Sun Earth WIMP DIRECTIONAL Programme • Q: What else can we do to identify a WIMP signal? • A: We can be more clever: S(A,ER) is in fact also function of recoil direction due to earth’s motion through DM halo. => Search for diurnal modulation to signal in directional detector. S(A,ER) => S(A,ER,) ~ exp(-((vEcos - vmin)/v0)2) D.N. Spergel, Phys. Rev. D 37 (1988) 1353

  44. WIMP “wind” (at Boulby)

  45. Galactic Halo Models • If a signal is seen then we can probe galactic halo parameters --> CDM streaming, infall, halo sphericity, co-rotation UKDMC simulated directional data for standard halo UKDMC simulated directional data for elongated halo (vz = 170 kms-1)

  46. 1.1 m SS vacuum vessel with internal Cu shielding, access flanges and silica calibration windows Multi-Wire Proportional Counter Readout DRIFT Project (UKDMC collaboration with US) The DRIFT-1 detector MWPC Occidental field cage UKDMC vessel UKDMC Gas and data Temple

  47. MWPC CS2- ions drift S CS2 gas E DRIFT Concept • New technique - Directional Recoil Identification From Tracks (DRIFT) uses low pressure (40 Torr) CS2 gas. • CS2 soaks up charge and carries it to read-out plane as CS2-. • High mass of ions limits transverse diffusion to < 1mm over 1m drift distance! • No need for magnet. • Discriminate with track-length.

  48. E DRIFT Concept Negative Ion Drift • Use CS2 + Ar, Xe at 10-80 Torr anode MWPC readout • Electrons from ionised tracks reversibly attach to CS2 and drift to anode CS2- ions drift WIMP • Longitudinal and transverse diffusion of ions is much less than for electrons --> typically < 1mm per m • No need for magnet Xe • Readout by conventional MWPC cathode An old idea E.W McDaniels et al., RSI 28 (1957) 864 H.R. Crane et al., RSI 32 (1961) 953

  49. recoil discrimination recoil discrimination alpha discrimination gammas gammas gammas C recoils alphas S recoils S recoil region (>90%) DRIFT Design • DRIFT: low pressure gaseous TPC • Recoil direction correlation • CS2 minimises diffusion • 1 foot cube detector @6keV • 99.9% gamma rejection • 95% alpha rejection (from wires) • DRIFT 1m3 Module under construction • 200m wire chamber 2cm pitch • 20m MWPC readout 2mm pitch • CS2+Xe,Ar at 10-80 Torr

  50. vessel DRIFT-1 Integration at Sheffield

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