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SIGN: Potential WIMP Detection using Pressurized Nobles

SIGN: Potential WIMP Detection using Pressurized Nobles. J.T. White Texas A&M University 5/16/07. Why Gaseous Nobles?. Original Motivation: Neon Electron mobility  possible S2/S1 discrimination  fiducial well defined Also: Room temperature operation Simpler purification

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SIGN: Potential WIMP Detection using Pressurized Nobles

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  1. SIGN:Potential WIMP Detection using Pressurized Nobles J.T. White Texas A&M University 5/16/07 PPC07 May 16, 2007

  2. Why Gaseous Nobles? • Original Motivation: • Neon • Electron mobility possible S2/S1 discrimination  fiducial well defined • Also: • Room temperature operation • Simpler purification • No leveling • No Cryo, etc … • NEW!! • S2/S1 Discrimination observed ! PPC07 May 16, 2007

  3. Halo Dark Matter: Starting Assumption WIMPs ρ ~ 0.3 GeV/cc <v> ~ 250 km/s @ earth PPC07 May 16, 2007

  4. WIMP Coherent Scattering (SI) WIMP 1 A E_recoil PPC07 May 16, 2007

  5. A2 Dependence of Recoil Spectra PPC07 May 16, 2007

  6. But, World is Radioactive! Gamma, beta U, Th, 40K, cosmogenics, etc, etc. . . . Nuclear / Electron recoil Discrimination Very important! Electron recoil PPC07 May 16, 2007

  7. S2/S1 discrimination in nobles Target Nuclei electron recoil Ionization Gamma background S2 nuclear recoil Scintillation S1 Background Discrimination WIMP or Neutron PPC07 May 16, 2007

  8. 12.7 mm 8 mm 12.7 mm Pressurized noble gasTest Cell Primary Scintillation S1 Sense Wire Field Tube TPB Prop. Scintillation S2 PTFE Sapphire Windows PPC07 May 16, 2007 S1 S2

  9. 4-PMT - 100 atm 4-PMT Test Cell Field tube PTFE reflector PPC07 May 16, 2007

  10. Sapphire Windows TPB coating PPC07 May 16, 2007

  11. Field Tuning Adjust field tube potential to optimize E-field uniformity along sense wire PPC07 May 16, 2007

  12. Event Waveforms (Ne-Xe example) Neutron Event Gamma Event Areas Same i.e. ionization same Primary (S1) Secondary (S2) PPC07 May 16, 2007

  13. Calibration Xe gas: 20 atm 122 keV Gamma (+ some 136) 12.7 mm 92 keV e- 30 keV x-ray Range 92 keV e- ~ 2 mm 8 mm Range 30 keV x-ray ~ 1 cm Range 30 keV e- ~ 0.2 mm PPC07 May 16, 2007 12.7 mm

  14. Calibration 122 keV Gamma 92 keV e- 30 keV x-ray unobserved PPC07 May 16, 2007

  15. Calibration 122 keV Gamma unobserved 92 keV e- 30 keV x-ray PPC07 May 16, 2007

  16. Calibration unobserved 122 keV Gamma 92 keV e- 30 keV x-ray Leff ~ 4.5% if Ws=76ev/ph Qgain ~ 1.2 p.e./e- (here) PPC07 May 16, 2007

  17. Neutron Scatteringw/ Mono-Energetic Neutrons En’ En, m θ Θ π Er, M Er  Ermax = (4 m M/(m+M)2) En Edge *** S – Wave  dN/dEr CM frame Er PPC07 May 16, 2007

  18. 4-MeV Proton Acceleratorat TAMU Duoplasmatron Ion source up to ~ 15 uA Tandem van de Graaff Achieved >1 uA on target  >5E6 n/sr/s Monochromatic neutrons up to 2 MeV using 7(Li(p,n)7Be reactions. PPC07 May 16, 2007

  19. Results Xe @ 20 atm ~ 300 psi PPC07 May 16, 2007

  20. Digression: Two-Phase Xenon Discrimination TAMU Test Cell AmBe Source S2/S1 Gammas Neutrons Centroid Separation ~ x 2 Acceptance box See Tom Shutt’s talk tomorrow !! PPC07 May 16, 2007 Recoil Energy (KeVr)

  21. Xe – 20 atm Nuclear Recoil response gammas S2/S1 neutrons Er_max ~ 27 keV PPC07 May 16, 2007

  22. S2 Spectra ? Co-57 data PPC07 May 16, 2007

  23. Xe – 20 atm NR Q & L yields Assuming Wi = 21.7 ev/e- 27 keV 39 keV Assuming Leff=4.5% PPC07 May 16, 2007

  24. Xe – S2/S1 Discrimination 23.7 116 21.6 107 Centroid Separation > X4 PPC07 May 16, 2007

  25. Results ArXe(0.5%) @ 50 atm ~ 750 psi PPC07 May 16, 2007

  26. ArXe(0.5%) – 50 atmNR Response ~ 15 events/ton/yr @ 10-45 pb/n Er threshold 40 keVr, Mx=100 GeV Er_max ~ 104 keV PPC07 May 16, 2007

  27. Ar Xe(0.5%) – Charge Yield Key! (Penning effect…) Average over E ~ 0.6  2.5 kV/cm 85 keV 120 keV PPC07 May 16, 2007

  28. ArXe(0.5%) – Light Yield Key! E ~ 0.6  2.5 kV/cm E ~ 0.6  2.5 kV/cm PPC07 May 16, 2007

  29. Results NeXe(0.5%) @ 100 atm 1600 psi PPC07 May 16, 2007

  30. Event Waveforms (Ne-Xe example) Neutron Event Gamma Event Areas Same i.e. ionization same Primary (S1) Secondary (S2) PPC07 May 16, 2007

  31. Nuclear Recoil Discrimination: S2 vs S1 Drift regions AmBe Higher field Lower field • S2/S1 field (and density) dependent for nuclear recoils • Gammas unaffected (Emin ~ 600 v/cm here) PPC07 May 16, 2007

  32. Primary Pulse Shape Discrimination PPC07 May 16, 2007

  33. S2/S1 AND Primary ShapeDiscrimination! Primary Pulse Shape Discrimination Gammas Neutrons PPC07 May 16, 2007

  34. NeXe(0.5%) – 100 atmNR Response ~ 1.8 evts/ton/yr @ 10-45 pb/n @ Er >= 40 keV Mx=100 GeV Red = 140 keVr Based on S2 Er_max ~ 140 keV PPC07 May 16, 2007

  35. NeXe(0.5%) – Q&L Yield E ~ 0.6  2 kV/cm E ~ 0.6  2 kV/cm PPC07 May 16, 2007

  36. Gas CsI Photocathode Light gain structure using WLS fibers SIGN conceptual design WIMP Cylinder S2 S1 Primary Ionization Prompt Scintillation PPC07 May 16, 2007 Photoelectrons

  37. Detector Concept Hub w/ WLS Fiber structure Composite Cylinder PPC07 May 16, 2007

  38. Drift Flow Steering Electrodes PPC07 May 16, 2007

  39. Gas Light Multiplier Concept Cirlex metallized plate, ~ 1mm holes Platinum coating – VUV transmitting VUV synthetic silica plates VUV -> blue phosphor coating WLS Fibers 100% e- transmission Fluorescence E/P>1 Lit – 0.006 p.e./vuv pho. PPC07 May 16, 2007

  40. 100 kg 20 atm Xe Prototype 3 m 0.6 m Shielding PMT SS Tube ~0.25 inch wall WLS Fibers CsI PPC07 May 16, 2007

  41. FutureComposite Vessels • Carbon, Kevlar wound • Some rated > 10000 psi ! • Used on mass transit (Methane)) • Used for Hydrogen fuel cells • On jets, spacecraft • DOT certified ! PPC07 May 16, 2007

  42. Shielding 4 m water shield See LUX discussion In Tom Shutt’s talk ~~4-5 m 10 modules 1 ton PPC07 May 16, 2007

  43. Plans–Phased Program Xenon • 100 kg Xe proto-experiment • Water shield • SS vessel • Only 300 psi … • Future –Neon @ 200 atm • WIMP Mass = ???? • Halo velocity dispersion = ???? • Number of “species” = ???? Even a caveman could do it Neon PPC07 May 16, 2007

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