1. J.T. White, TAMUPPC07 May 16, 2007 SIGN: Potential WIMP Detection using Pressurized Nobles J.T. White Texas A&M University 5/16/07

2. J.T. White, TAMUPPC07 May 16, 2007 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 !

3. J.T. White, TAMUPPC07 May 16, 2007 Halo Dark Matter: Starting Assumption ρ ~ 0.3 GeV/cc ~ 250 km/s @ earth WIMPs

4. J.T. White, TAMUPPC07 May 16, 2007 WIMP Coherent Scattering (SI) 1 A WIMP E_recoil

5. J.T. White, TAMUPPC07 May 16, 2007 A 2 Dependence of Recoil Spectra

6. J.T. White, TAMUPPC07 May 16, 2007 But, World is Radioactive! Gamma, beta Electron recoil U, Th, 40K, cosmogenics, etc, etc.... Nuclear / Electron recoil Discrimination Very important!

7. J.T. White, TAMUPPC07 May 16, 2007 S2/S1 discrimination in nobles Gamma background electron recoil Target Nuclei nuclear recoil WIMP or Neutron Scintillation Ionization Background Discrimination S2 S1

8. J.T. White, TAMUPPC07 May 16, 2007 Pressurized noble gas Test Cell 12.7 mm 8 mm Primary Scintillation S1 Prop. Scintillation S2 S1S2 PTFE Sapphire Windows Field Tube Sense Wire TPB

9. J.T. White, TAMUPPC07 May 16, 2007 4-PMT - 100 atm 4-PMT Test Cell PTFE reflector Field tube

10. J.T. White, TAMUPPC07 May 16, 2007 Sapphire Windows TPB coating

11. J.T. White, TAMUPPC07 May 16, 2007 Field Tuning Adjust field tube potential to optimize E-field uniformity along sense wire

12. J.T. White, TAMUPPC07 May 16, 2007 Event Waveforms (Ne-Xe example) Neutron Event Gamma Event Areas Same i.e. ionization same Secondary (S2) Primary (S1)

13. J.T. White, TAMUPPC07 May 16, 2007 Calibration 122 keV Gamma (+ some 136) 92 keV e- 30 keV x-ray 12.7 mm 8 mm Range 92 keV e- ~ 2 mm Xe gas: 20 atm Range 30 keV e- ~ 0.2 mm Range 30 keV x-ray ~ 1 cm

14. J.T. White, TAMUPPC07 May 16, 2007 Calibration 122 keV Gamma 92 keV e- 30 keV x-ray unobserved

15. J.T. White, TAMUPPC07 May 16, 2007 Calibration 122 keV Gamma 92 keV e- 30 keV x-ray unobserved

16. J.T. White, TAMUPPC07 May 16, 2007 Calibration 122 keV Gamma 92 keV e- 30 keV x-ray Leff ~ 4.5% if Ws=76ev/ph Qgain ~ 1.2 p.e./e- (here) unobserved

17. J.T. White, TAMUPPC07 May 16, 2007 Neutron Scattering w/ Mono-Energetic Neutrons θ Er, M En, m En’ Θ  πΘ  π Er  Ermax = (4 m M/(m+M) 2 ) En S – Wave  Er dN/dEr CM frame Edge ***

18. J.T. White, TAMUPPC07 May 16, 2007 4-MeV Proton Accelerator at TAMU Monochromatic neutrons up to 2 MeV using 7 (Li(p,n) 7 Be reactions. Tandem van de Graaff Duoplasmatron Ion source up to ~ 15 uA Achieved >1 uA on target  >5E6 n/sr/s

19. J.T. White, TAMUPPC07 May 16, 2007 Results Xe @ 20 atm ~ 300 psi

20. J.T. White, TAMUPPC07 May 16, 2007 Digression: Two-Phase Xenon Discrimination Gammas Neutrons Centroid Separation ~ x 2 Recoil Energy (KeVr) S2/S1 Acceptance box See Tom Shutt’s talk tomorrow !! TAMU Test Cell AmBe Source

21. J.T. White, TAMUPPC07 May 16, 2007 Xe – 20 atm Nuclear Recoil response S2/S1 Er_max ~ 27 keV gammas neutrons

22. J.T. White, TAMUPPC07 May 16, 2007 S2 Spectra Co-57 data ?

23. J.T. White, TAMUPPC07 May 16, 2007 Xe – 20 atm NR Q & L yields 39 keV 27 keV Assuming Wi = 21.7 ev/e- Assuming Leff=4.5%

24. J.T. White, TAMUPPC07 May 16, 2007 Xe – S2/S1 Discrimination 23.7116 Centroid Separation > X4 21.6107

25. J.T. White, TAMUPPC07 May 16, 2007 Results ArXe(0.5%) @ 50 atm ~ 750 psi

26. J.T. White, TAMUPPC07 May 16, 2007 ArXe(0.5%) – 50 atm NR Response Er_max ~ 104 keV ~ 15 events/ton/yr @ 10 -45 pb/n Er threshold 40 keVr, Mx=100 GeV

27. J.T. White, TAMUPPC07 May 16, 2007 Ar Xe(0.5%) – Charge Yield 120 keV 85 keV Average over E ~ 0.6  2.5 kV/cm Key! (Penning effect…)

28. J.T. White, TAMUPPC07 May 16, 2007 ArXe(0.5%) – Light Yield E ~ 0.6  2.5 kV/cm Key!

29. J.T. White, TAMUPPC07 May 16, 2007 Results NeXe(0.5%) @ 100 atm 1600 psi

30. J.T. White, TAMUPPC07 May 16, 2007 Event Waveforms (Ne-Xe example) Neutron Event Gamma Event Areas Same i.e. ionization same Secondary (S2) Primary (S1)

31. J.T. White, TAMUPPC07 May 16, 2007 Nuclear Recoil Discrimination: S2 vs S1 Drift regions Higher field  S2/S1 field (and density) dependent for nuclear recoils  Gammas unaffected (Emin ~ 600 v/cm here) Lower field AmBe

32. J.T. White, TAMUPPC07 May 16, 2007 Primary Pulse Shape Discrimination

33. J.T. White, TAMUPPC07 May 16, 2007 S2/S1 AND Primary Shape Discrimination! Primary Pulse Shape Discrimination Gammas Neutrons

34. J.T. White, TAMUPPC07 May 16, 2007 NeXe(0.5%) – 100 atm NR Response Er_max ~ 140 keV Red = 140 keVr Based on S2 ~ 1.8 evts/ton/yr @ 10 -45 pb/n @ Er >= 40 keV Mx=100 GeV

35. J.T. White, TAMUPPC07 May 16, 2007 NeXe(0.5%) – Q&L Yield E ~ 0.6  2 kV/cm

36. J.T. White, TAMUPPC07 May 16, 2007 SIGN conceptual design Gas CsI Photocathode Light gain structure using WLS fibers WIMP Primary Ionization Prompt Scintillation Photoelectrons Cylinder S2S1

37. J.T. White, TAMUPPC07 May 16, 2007 Detector Concept Composite Cylinder Hub w/ WLS Fiber structure

38. J.T. White, TAMUPPC07 May 16, 2007 Drift Flow Steering Electrodes

39. J.T. White, TAMUPPC07 May 16, 2007 Gas Light Multiplier Concept Cirlex metallized plate, ~ 1mm holes VUV synthetic silica plates Platinum coating – VUV transmitting VUV -> blue phosphor coating WLS Fibers 100% e- transmission Fluorescence E/P>1 Lit – 0.006 p.e./vuv pho.

40. J.T. White, TAMUPPC07 May 16, 2007 100 kg 20 atm Xe Prototype 3 m 0.6 m Shielding CsI PMT SS Tube ~0.25 inch wall WLS Fibers

41. J.T. White, TAMUPPC07 May 16, 2007 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 !

42. J.T. White, TAMUPPC07 May 16, 2007 Shielding 10 modules  1 ton ~~4-5 m 4 m water shield See LUX discussion In Tom Shutt’s talk

43. J.T. White, TAMUPPC07 May 16, 2007 Plans – Phased Program 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 Xenon Neon