XENON Experiment Development of Xe Dual Phase Prototype for Dark Matter Detection

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1 XENON Experiment Development of Xe Dal Phase Prototype for Dark Matter Detection Brown University, Department of Physics see information at Gaitskell

2 XENON Dark Matter Collaboration Brown University Richard Gaitskell Peter Sorensen Colmbia University Elena Aprile (PI), Edward Baltz,Alessandro Crioni Karl-Ldwig Giboni,Chck Hailey,Lam Hi Masanori Kobayashi,Pawel Majewski,Kaixan Ni Rice University Uwe Oberlack,Omar Vargas Princeton University John Kwong, Changgo L, Kirk McDonald, Michael Niemack, Tom Shtt Lawrence Livermore National Laboratory William Craig Stockholm University, Sweden Vladimir Peskov

3 Low Thresholds Vital Very Typical WIMP Signal Graph shows integrated event rates for E>Er for Xe (green), Ge (red) and S (ble) Large nclei enhanced by nclear coherence, however, in reality <<A 2 Ú E r dn de Xe E th =16 kevr gives 1 event/kg/day Example cross-section shown is at crrent (90%) exclsion limits of existing experiments Xe WIMP rate for Er > 16 kevr is (1) within factor 2 of maximm achievable rate (Er>0) (2) eqivalent kg/kg to low threshold Ge detector (3) 5x better kg/kg than light ncles (e.g. S in CS 2 ) XENON Dark Matter - EPS HEP Aachen - Jl 2003

4 XENON Event Discrimination: Electron or Nclear Recoil? Within the xenon target: Netrons, WIMPS => Nclear recoils => Scintillation, little Ionisation g,, e-, m,, (etc) => Electron recoils => Scintillation, sbstantial Ionisation Ionisation electrons are drifted by field E GC and extracted to the gas phase by field E AG. De to increase in field E AG arond anode wires electrons increase kinetic energy => proportional scintillation via collisions with gaseos Xe. The reslt is a large proportional light signal, which gives event-by-event discrimination against backgrond. Gaitskell Time Proportional ~1 µs width µs depending on depth Primary ~40 ns width Light Signal UV ~175 nm photons e - e - e - - e - e - e - - e - e - e - - Gas phase Electron Drift ~2 mm/µs Liqid phase PMT Array (not all tbes shown) E AG E GC Anode Grid Cathode E AG > E GC Interaction (WIMP or Electron) Liq. Srface

5 Gaitskell Addition of CsI Photocathode at base A Tertiary signal can be generated from absorbing primary photons into CsI photocathode Efficiency very good - Geometry Solid Angle - In Liq (No TIF transmission loss) - CsI QE 30% Note: 16 kev nclear recoil: 200 photons before applying efficiencies for geometry and PMT QE. Also ionization signal 7-20 electrons (assmes high field 8 kv/cm) Time CsI Tertiary 150 µs (if 30 cm chamber) Primary ~40 ns width Light Signal UV ~175 nm photons CsI is possible option being evalated for prototype design e - Gas phase PMT Array (not all tbes shown) e - E AG E GC Anode Grid CsI Cathode E AG > E GC Interaction (WIMP or Electron) Liq. Srface

6 Available Signal in Liq. Xe (# of photons & electrons for 1 kev event) Smmary SUMMARY OF PARAMETERS FROM EXISTING MEASUREMENTS Zero Field High Field 0 V/cm 8 kv/cm GAMMA EVENT - 1 kev electron eqivalent energy UV Photons UV UV Electrons+Ions [60-75 elec] elec NUCLEAR RECOIL EVENT - 1 kev recoil energy UV Photons UV 11.6 UV Electrons+Ions [12-18 elec] elec EFFECTIVE (NR/GAMMA) "QUENCHING FACTOR" UV Photons 20-25% 30-50% Electrons+Ions [20-25%] 0.8-2% The ranges shown reflect spread in existing experimental measrements Note that the table considers signal from either 1 kev gamma or nclear recoil event 60 excitations / kev is eqivalent to ~16 ev / excitation Zero field electron-ion # s in [ ] are inferred, bt are signal is not measred (extracted) directly XENON Dark Matter - EPS HEP Aachen - Jl 2003

7 The XENON Experiment : Design Overview Dal Phase Liq/Gas Xe The XENON design is modlar. Mltiple 3D position sensitive LXeTPC modles, each with a 100 kg active Xe mass --> 1-tonne scale experiment. The 100 kg fidcial LXe volme of each modle is shielded by additional 50 kg LXe. Active shield very effective for charged and netral backgrond rejection. Colmbia, Brown, Livermore, Princeton, Rice. Fnded Sept Crrently - R&D towards 10 kg prototype. Deployment goal: 100 kg XENON Dark Matter - EPS HEP Aachen - Jl 2003

8 The Colmbia LXeTPC - DM Prototype 0 30 kg XENON Dark Matter - EPS HEP Aachen - Jl 2003 LXeGrit ballon g telescope 30 kg active Xe mass 20 x 20 cm 2 active area 8 cm drift with 4 kv/cm Charge and Light readot 128 wires/anodes ADC 4UV PMTs

9 XENON R&D Program Single Phase (Liq) cm Q drift (Qamp readot) Testing different PMTs (Mech/QE/Elec) Data for Light Collection Model (inclded Teflon reflectors) Check Xe Contamination of components DAQ Config. Dal phase, 1 cm Q drift (Prop scin readot) PMT in gas Stdy Electric Fields Light Collection Extra CsI Cathode Additionally 10 cm drift length measrements Q drift good with teflon Demonstration of good electron drift with Teflon Also new setps being bilt at Brown, Princeton, Rice Constrction of new Colmbia 10 kg prototype nderway 7 PMTs Plse-tbe cooled cryostat XENON Dark Matter - EPS HEP Aachen - Jl 2003

10 Two Phase System (Colmbia/ K. Ni) 207Bi Primary Scintillation 207Bi Proportional Light (Q) Signal size increases by 6x after ptting in Teflon XENON Dark Matter - EPS HEP Aachen - Jl 2003

11 Single Phase Jst add Liq Xe & 662 kev g s XENON Dark Matter - EPS HEP Aachen - Jl 2003

12 Xenon Prity Need to drift charge >>1 cm places most severe constraint on Xe prity Electronegative imprities <1 ppb level This is more stringent that levels reqired for observation of UV scintillation only Rotinely achieving reqired levels Using SAES Getter (Also evalating Ti arc getter) Chamber baked ~70 degc / pipes somewhat hotter Now evalating contamination arising from varios new components being introdced Steps to redce contamination e.g. PMT bases -> Ceramic -> Kapton Cables replaced / PMT enclosres scrbbed XENON Dark Matter - EPS HEP Aachen - Jl 2003

13 Hamamats PMT Selection (Baseline design) Model Photo (not same scales) Dimension & QE Radioactive Backgrond * [mbq/tbe] Comment R6041 ø5 cm x 4 cm QE 5-8% 6000 mbq (Dominated by glass seal at base) Specifically designed for ops in LiqXe TPC R9288 ø5 cm x 4 cm QE 20% 150 mbq (Use of Kovar for most of base) Evoltion of 6041 R8520 (2.5 cm) 2 x3.5cm QE >20% 15 mbq Sqare/qad anodegood fill factor. Colmbia tested at 150K/4 atm R8778 ø5 cm x 12 cm QE 26% 31 mbq (expect frther improvement) Designed for XMASS. Colmbia tested at 150K/4 atm XENON Dark Matter - EPS HEP Aachen - Jl 2003 * 1 mbq/ø5cm project goal

14 Charge readot Advanced readot schemes - Smmary GEMs (Rice) MWPC (Princeton) Light detectors Brle MCP (Brown) Constrcted new cryogenic hosing for MCPs Expect first test in Liq Xe in Ag Hamamats low-backgrond PMTs Qartz windows, limited ceramics Backgronds 10 mbq/pmt x better than standard. LAAPD (Brown) (A. Bondar et al., prepr. physics/ ) CsI (Colmbia) XENON Dark Matter - EPS HEP Aachen - Jl 2003

15 Removing Kr (+Ar) with chromatographic adsorption Adsorption constant adsorption constant J.R. Michaels and N.R. Morton., 12th AEC Air Cleaning Conference, Xe Kr Ratio > K 85 Kr in Xe Xe Commercial grade 5-10 ppm Kr Projection for cm 2 sensitivity needs 100 ppt Kr Goal 1 ppt possible Chromatographic separation: Kr moves throgh colmn faster Use He (or Ne) carrier gas Princeton Grop concentration 1/Temp XENON Dark Matter - EPS HEP Aachen - Jl 2003 Position in colmn

16 10 kg Dal Phase Prototype System Constrction started of 10 kg dal phase system (assemble Ag 03) Temperatre Control Using Plse Tbe Cooler Mechanical region for 7 x ø5cm photodetectors - can accommodate different length PMTs discssed Fidcial / Drift Region 10 cm deep Note: Materials are not low backgrond selected (this is next phase) XENON Dark Matter - EPS HEP Aachen - Jl 2003

17 XENON Collaboration Smmary Rotinely Operating Two Xe Test Rigs at Colmbia Additional rigs being constrcted at Rice / Princeton / Brown Testing Components for 10 kg Prototype Baseline Design Two phase demonstrated / necessary fields being stdied Collecting Data for Light Propagation Monte Carlos PMT Selection - improvements in QE & radioactive backgronds Xe Prity - Q drift - rotinely achieved (bt often pertrbed when inserting new components) Additional Technologies being investigated Photodetectors / Alternative Q readot Bilding 10 kg Prototype Two phase with 7 PMTs and 10 cm drift Netron measrement and gamma discrimination Test additional technologies/materials needed for low backgrond version XENON Dark Matter - EPS HEP Aachen - Jl 2003

18 Crrent & Next Generation Experiments & SUSY Theory Range Edelweiss (Jne 2003) ~0.25 event/kg/d ~1 event/kg/yr ~ 1 event/100 kg/yr XENON Dark Matter - EPS HEP Aachen - Jl 2003