July 2001 Neil Spooner UKDM Programme Update on NaI, ZEPLIN and DRIFT Neil Spooner, University of Sheffield

July 2001 Neil Spooner New Caverns More lab space than Soudan 50 m £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 New U/G Infrastructure 2000

July 2001 Neil Spooner 50m Stub 2 Stub 2a,3 ‘H’ Area JIF Area Boulby U/G Facilities

July 2001 Neil Spooner ~1500m 2 new lab space Experimental Halls Clean Bay Control Room Workshop DRIFT Bay Store Workshop Mess Coms/Elecs. Changing Control Room Clean Clean Bay Running boards 6m 20m 47m 14m 8m 20m Transfer 3.8m Laboratories Clean rooms Workshop Mess Fibre optic/Enet New JIF Underground Facility

July 2001 Neil Spooner ~ 1500 m 2 new space New Area Under Construction

July 2001 Neil Spooner Main experimental hall will have 4-5m FLAT room DRIFT 1 site DRIFT Area Construction

July 2001 Neil Spooner New Surface Laboratory

July 2001 Neil Spooner Contact me: Neil Spooner - Facility Management BoardInternational Boulby Research Board Facility manager and staff Projects co-ordinator Institute for Underground Science Plenty of new lab space available Call For Proposals

July 2001 Neil Spooner NaI small array 20 kg NAIAD high rate array 50 kg UK-Saclay 20 kg NAIAD array existing ramp down ZEPLIN-I single phase PSD 4 kg ZEPLIN-II ion-scint two phase Xe 30 kg ZEPLIN-III Ion-scint two phase Xe high field 6 kg ZEPLIN array under construction existing ZEPLIN-MAX ion-scint two phase Xe 1000 kg MULTINATIONAL concept under construction DRIFT 1 directional 1 m 3 DRIFT array DRIFT 10 directional 10 m 3 MULTINATIONAL concept Boulby Dark Matter Projects

July 2001 Neil Spooner QMW: J. C. Barton University of Surrey: E. Morton, P. Sellin CERN/Padova: A PietropauloITEP: 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 ParkColumbia: C Hailey, J Hong, E Aprile, A Castellina UCSD: K Griest, G Masek, K BucklandTemple University: C J Martoff, P Ambrozewicz, E Kaczanowicz 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 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 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 Torino: P Picchi, L Periale, G Mannocchi, C Taricco, C Castagnoli, A Curioni Saclay: G. Gerbier Occidental College: D Snowden-Ifft, T Ohnuki, N Villaume, J Burwell LLNL: B Craig, M J Lehner UKDMC Boulby Dark Matter Collaboration (BDMC) People Involved in Dark Matter

July 2001 Neil Spooner Boulby NAIAD Programme status and programme Low-A target (Na) for WIMP masses < 200 GeV/c 2 to reach 0.1/kg/dMotivation Pulse shape discrimination and known technology that can be scaled up --> Complements liquid Xe high-A --> satisfies requirement for (i) recoil identification and (ii) diagnostic array capability Information relevant to DAMA using the same target, NaI

July 2001 Neil Spooner UKDMC NaI - PSA low activity silica light guides & PMT shield double zone refined NaI(Tl) crystal PMT Example time constant distributions for new crystal DM72 showing log gauss neutron and compton fits and data.  E keV neutron Compton 1996 limit from DM46 spin-independent Schematic of early NaI detector e.g. DM46 NaI(Tl) Integrated Pulse- Shape

July 2001 Neil Spooner Following improvement to DM46 (5 kg) - discovery of fast events in NaI Data (  E keV) calibration Example  histogram for DM46 showing anomalous events Typical fast event energy distributions in various crystals of different geometry NaI Anomalous Events (1998) Anomaly

July 2001 Neil Spooner UKDMC NaI + Saclay Collaboration with Saclay to run a “DAMA” crystal at Boulby very similar spectrum of fast events seen again RESULT this despite very different manufacture and geometry UKDMC spectrum anomalous event spectra in NaI Saclay (“DAMA”) spectrum

July 2001 Neil Spooner DAMA PSD UKDMC anomalous event spectra Limit on anomalous events from DAMA old PSD data

July 2001 Neil Spooner Many underground and laboratory tests performed lead/copper shielding water shielding paraffin light guide silica light guides not internal activity too fast for neutrons RESULT not external betas…. most likely surface implanted outgoing alphas (a) Example  distribution for DM26 exposed to external low E alphas alphasgammas  E keV NaI Anomalous Events (1998) Anomaly seen in many crystals: Different manufacture, Different aspect ratio, Different history

July 2001 Neil Spooner Outgoing Surface Alphas? Outgoing  events –Radon implantation? –Surface contamination? Supported by recent surface treatment results ~0.005ppb U

July 2001 Neil Spooner Identification of the events Confirmed with CsI - easier to use unencapsulated than NaI anomalous events CsI Test (DM71) known internal alphas after surface polish prior to surface polish CsI

July 2001 Neil Spooner UKDMC spectrum Saclay (“DAMA”) spectrum DM74 limit on fast event spectrum UKDMC spectrum Saclay (“DAMA”) spectrum DM74 limit on fast event spectrum anomalous event spectra in NaI anomalous events reduced in NaI RESULT BUT at least 3-4 months exposure to Rn would be needed! - difficult to explain Confirmed with unencapsulated NaI (DM74)  distribution for pre-polished unencapsulated crystal DM74 after 5 mns operation no fast events within stat Identification of the events Are the fast events in any way related to the DAMA result?

July 2001 Neil Spooner NAIAD Design dry nitrogen or mineral oil Unencapsulated units for 5-10 kg NaI crystals built OFHC box PTFE crystal cage crystal

July 2001 Neil Spooner NAIAD Programme - H-Area 35 kg Unencapsulated surface controlled NaI 15 kg Encapsulated high light yield NaI 10 kg Saclay crystal NaI unencapsulated crane glove box to JIF area H area map H 1 H 2 Control room

July 2001 Neil Spooner NAIAD Installation

July 2001 Neil Spooner NAIAD Preliminary Results

July 2001 Neil Spooner Boulby Xenon Programme Xe * +Xe Xe 2 * Triplet 27ns Singlet 3ns 2Xe 175nm Excitation (recombination) Xe ** + Xe Xe 2 + +e - Xe + +Xe Ionisation Nuclear/Electron Recoil three discrimination techniques (1) scintillation pulse shape (2) ionisation-scintillation - low field- (3) ionisation-scintillation - high field, low threshold - single phase Xe two phase Xe liquid gas ICARUS-UCLA ITEP Doke group (Japan) DAMA World expertise UKDMC Columbia

July 2001 Neil Spooner Boulby Xenon Programme ZEPLIN-I single phase PSD 4 kg ZEPLIN-II ion-scint two phase Xe 30 kg ZEPLIN-III Ion-scint two phase Xe high field 6 kg ZEPLIN ZEPLINarray under construction running demonstrate basic discrimination with PSD - set first limits basic ionisation-scintillation and high target mass - improve by x10 - UCLA concept ionisation-scintillation and high field - ultimate discrimination, low threshold - ZEPLIN-MAX ion-scint two phase Xe 1000 kg new (5 years) A multinational programme : Involved in programmes: UCLA, CERN/Padova, Torino, ITEP, Coimbra, Columbia, RAL, ICSTM, Sheffield

July 2001 Neil Spooner UKDMC Xenon - ZEPLIN I Xe * +Xe Xe 2 * Triplet 27ns Singlet 3ns 2Xe 175nm Xe ** + Xe Xe 2 + +e - (recombination) Xe + +Xe

July 2001 Neil Spooner ZEPLIN I Underground Pb shielding Top of ZEPLIN I veto Boulby stub 2 laboratory xenon purification Stable operation demonstrated Counts vs. time Xe temp vs. time room temp vs. time

July 2001 Neil Spooner ZEPLIN Operations at Boulby

July 2001 Neil Spooner ZEPLIN I Laboratory tests Compton veto (1 ton PXE) found to have ~50 keV threshold PMT background events rejected by turret fiducial cuts as expected 137 Cs events origin is where all 3 PMTs record identical signals turret events rejected by asymmetry cut

July 2001 Neil Spooner Light collection exceeds design spec of 1 pe/keV pe/keV keV Z I data theory Up to 50% difference in neutron and gamma time constants tau (ns) keV ZEPLIN I Laboratory tests

July 2001 Neil Spooner ZEPLIN I Discrimination Gamma source Neutron source 10-20keV 20-30keV  (ns)  (ns) n 

July 2001 Neil Spooner ZEPLIN I - Results 85 Kr < atoms/atom Predictions for 1 year

July 2001 Neil Spooner Light Yield –Increases at low energy Spatial Uniformity – 137 Cs Source Data Theory ZEPLIN I Laboratory tests

July 2001 Neil Spooner ZEPLIN I - Predicted Limits

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

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

July 2001 Neil Spooner ZEPLIN-MAX A BDMC multinational programme Final design by mid 2002 Recoil Discrimination Construction Options being explored: (I) single unit, (II) 4 units, (III) modular (IV) mass + low threshold units RESULT: (a) attain /kg/d, (b) diagnostic array with complementary techniques 3 modules 80 kg target 4 sub- units shielding One possibility ZEPLIN - 1 ton Concept

July 2001 Neil Spooner PMT Removal for Scale-Up? Liquid Xe Xe Gas He Cooling GEMs CsI PTFE Reflector CsI Field Shaping Rings nucl.rec. elec.rec. CsI photocathodes in LXe: E.Aprile, NIMA 338 (1994), 328; NIMA 343 (1994), 121. GEM phototubes in noble gases: v, NIMA, 443 (2000), 164. Sheffield test cell

July 2001 Neil Spooner GEM Prototype Target High or low field operation In-house CsI photocathode production GEMs of Sheffield design from CERN

July 2001 Neil Spooner GEM Rig

July 2001 Neil Spooner ZEPLIN locations at Boulby Stub 2 ZEPLIN-I ZEPLIN-MAX ZEPLIN-III ZEPLIN-II JIF Facility

July 2001 Neil Spooner NaI 1996 limit ZEPLIN 2002/3 ZEPLIN I/II 2003 ZEPLIN II/III WIMP-nucleon cross-section, pb WIMP mass GeV CDMS II CRESST II ZEPLIN-MAX 2006 ZEPLIN predictions based on prototype tests and operation of ZEPLIN I ZEPLIN-XENON Predictions

July 2001 Neil Spooner DIRECTIONAL Programme Q: What else can we do to identify a WIMP signal? We can be more clever: S(A,E R ) is in fact also function of recoil direction due to earth’s motion through DM halo. =>A: We can be more clever: S(A,E R ) 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 ~30 kms -1 ~220 kms -1 Sun Earth Jun. 2nd WIMP S(A,E R ) => S(A,E R,  ) ~ exp(-((v E cos  - v min )/v 0 ) 2 ) D.N. Spergel, Phys. Rev. D 37 (1988) 1353

July 2001 Neil Spooner WIMP “wind” (at Boulby)

July 2001 Neil Spooner Galactic Halo Models UKDMC simulated directional data for standard halo UKDMC simulated directional data for elongated halo (v z = 170 kms -1 ) If a signal is seen then we can probe galactic halo parameters --> CDM streaming, infall, halo sphericity, co-rotation

July 2001 Neil Spooner DRIFT Project MWPC Occidental Temple SS vacuum vessel with internal Cu shielding, access flanges and silica calibration windows vessel UKDMC The DRIFT-1 detector 1.1 m Multi-Wire Proportional Counter Readout field cage Gas and data UKDMC (UKDMC collaboration with US)

July 2001 Neil Spooner DRIFT Concept New technique - Directional Recoil Identification From Tracks (DRIFT) uses low pressure (40 Torr) CS 2 gas. CS 2 soaks up charge and carries it to read- out plane as CS 2 -. High mass of ions limits transverse diffusion to < 1mm over 1m drift distance! No need for magnet. Discriminate with track-length. CS 2 gas E CS 2 - ions drift S MWPC

July 2001 Neil Spooner DRIFT Concept Negative Ion Drift An old idea E.W McDaniels et al., RSI 28 (1957) 864 H.R. Crane et al., RSI 32 (1961) 953 E CS 2 - ions drift Xe WIMP anode MWPC readout cathode Longitudinal and transverse diffusion of ions is much less than for electrons --> typically < 1mm per m No need for magnet Readout by conventional MWPC Use CS 2 + Ar, Xe at Torr Electrons from ionised tracks reversibly attach to CS 2 and drift to anode

July 2001 Neil Spooner DRIFT: low pressure gaseous TPC –Recoil direction correlation –CS 2 minimises diffusion 1 foot cube –99.9% gamma rejection –95% alpha rejection (from wires) DRIFT 1m 3 Module under construction –200  m wire chamber 2cm pitch –20  m MWPC readout 2mm pitch CS 2 +Xe,Ar at Torr DRIFT Design gammas recoil discrimination C recoils S recoils gammas recoil discrimination gammas alphas S recoil region (>90%) alpha discrimination

July 2001 Neil Spooner DRIFT-1 Integration at Sheffield vessel

July 2001 Neil Spooner 1 m DRIFT-1 Detector

July 2001 Neil Spooner DRIFT-1 Integration at Sheffield

July 2001 Neil Spooner DRIFT-1 Predicted limits Full background audit for DRIFT-1 completed (tests and MCs) a background of ~ 5 counts per year per m 3 is feasible DRIFT-1 can yield a limit below DAMA CONCLUSION DRIFT-1 could just detect a directional signal at pb 3 m 3 yr 30 WIMP events 80 WIMP events

July 2001 Neil Spooner DRIFT 1 site Installation Aug 01 Part of 1500 m 2 new facility at Boulby mwe depth DRIFT 1 - Installation Aug 01

July 2001 Neil Spooner DRIFT-10, towards 1 ton a BDMC - multinational programme --> need 1 ton to get enough counts at minimum SUSY DRIFT-1 DRIFT-10 1 ton CS 2 Xe DRIFT-MAX - 1 Ton gas

July 2001 Neil Spooner Summary DAMA NaI annual modulation as objective WIMP or fluctuating low energy noise? UKDMC ‘anomalous events’ as surface alphas? Seen in Saclay (DAMA) crystal CDMS recoil limit (almost) excludes DAMA Subtraction of neutron signal Several detectors becoming sensitive at pb Many more direct searches underway to reach ≈10 -8 pb Indirect searches reaching sensitivities to exclude models WIMPs (10 -9(or -12) pb < s cp < pb, 50 GeV < m <600 GeV)