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J.T. White Texas A&M University

SIGN ( S cintillation and I onization in G aseous N eon) A WIMP Detector based on Gaseous Neon. J.T. White Texas A&M University. Institutions: TAMU, UCLA. The Future of Dark Matter Detection University of Chicago, Dec. 9-10, 2004. WIMP – Neon Interaction. WIMP. 1 ton, 1.e -8 pb/n.

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J.T. White Texas A&M University

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  1. SIGN (Scintillation and Ionization in Gaseous Neon) A WIMP Detector based on Gaseous Neon J.T. White Texas A&M University Institutions: TAMU, UCLA The Future of Dark Matter Detection University of Chicago, Dec. 9-10, 2004

  2. WIMP – Neon Interaction WIMP 1 ton, 1.e -8 pb/n Ne Nuclear Recoil F(Q2) ~ 1

  3. Inelastic Response of Recoiling Nucleus Efficiency Lindhard Lindhard * Threshold Effect

  4. Observable Spectra 1 ton, 1.e - 8pb/nucleon Recoil Spectra IF ~ALL Lindhard Energy is observed with 100% efficiency.

  5. Neon Gas P >= 100 atm + Xenon 0.1-0.5 % *** key trick*** CsI Photocathode Sense & Field wires WLS fibers (optional) SIGN concept WIMP Cylinder e.g. Diameter ~ 40 cm Length ~ 5 m Mass >~ 50kg @ 100 atm Primary Ionization Prompt Scintillation Photoelectrons

  6. Effect of Xenon doping !!! → some Ne+ + e- 3/2 1/2 Ne+ + Xe → Ne+Xe → NeXe+ + 134nm then 3/2 1/2 or Ne+ + e- → Ne* (recomb., pressure dep.?) → and some Ne* Ne* + Ne → Ne2* → 2Ne + 80 nm 80 nm + Xe →Xe+ + e- then (in a few microns) Ne* + Xe → Ne*Xe → Ne + Xe+ + e- or Some Xe+ + e- →Xe* and some Xe* directly produced Xe* + Xe → Xe*Xe → 2Xe + 175 nm Note ! Nuclear Recoils: mostly Ne*(?), Electron: mostly Ne+

  7. Two Big Questions!! • Is a detector operating at 100 atm mechanically feasible?Is it dangerous? • Is it possible to operate a proportional counter with P >~ 100 atm ?Usually wire chambers operate at >~ 1000 V – does this mean one would have to operate >~ 100,000 V ?

  8. Safety? • Composite cylinders • Carbon, Kevlar wound • Some rated > 10000 psi ! • Used on mass transit (Methane)) • Used for Hydrogen fuel cells • On jets, spacecraft • DOT certified ! • Perhaps cast in acrylic blocks

  9. Off-the-shelf Module ~ 3 m 43 cm diameter 300 cm length 6000 psi = 408 atm ~ 40 cm spun aluminum carbon fiber winding

  10. Signal at P > 100 atm? Test Cell Electrofluorescence Mostly 175 nm 100 atm NeXe(.5%) PMT Sapphire +HV - HV Charge Amp Radioactive source

  11. High Pressure Test Cell PMT Support Cell Charge Amp Argon Flow

  12. 55Fe Signal Primary ~2 us Light Photoelectric from SS QE ~ .02% @175 nm Secondary Charge charge preamp signal - note kink

  13. 55Fe Spectra Light Charge

  14. 241Am Alpha Primary Secondary Light Charge Shaping Amp 1 us shaping

  15. Answers to Two Big Questions 1) Yes, safe enough for the public! 2) Yes, at V ~ 5000 V, tube diameter ½ in, 125 um sense wire - Charge gain ~~ 300 (preliminary) - Light Gain ~~ 2000 photons/e- (preliminary) at 175 nm!

  16. Signal Feedback of ionization signal from CsI – perhaps saturated. Primary Ionization Feedback of Scintillation signal from CsI – amplified! Scintillation From CsI Gating Pulse Max Drift time

  17. Drift Field and Gating Drift Trajectories Equi-potentials CAN Gate Field Wires Between Sense Wires – few KV !

  18. SIGNConceptual Design MgF2- coated LEXAN light guide WLS Fibers Coated With TPB PMT Both Ends Charge Readout -Both Ends -Can sum wires

  19. Structure of Inner Cylinder Stainless Steel Inner Cylinder Hollow, Stiff Sense wire TPB VUV to blue Field/Gating Wires Blue-Green WLS Fiber

  20. If Discrimination, etc  Potential Sensitivity 1 ton, 1 yr 100 tons, 1 yr

  21. Annual Modulation Sensitivity? 1 ton neon 1 x 10-6 pb/nucleon Bk=0.01evts/keV/kg/day Rx = ∑ 2 cos(wt) D(t) Ry = ∑ 2 sin(wt) D(t) 90% Rx Ry cosine projection method –Freese, Friedman, Gould, PRD 37 (12)(1987) 3388-3405

  22. WIMP sensitivity estimate Using Lindhard + Threshold Effect No Discrimination Applied

  23. Other Applications? -Supernova Earth ~ 10 kpc E ~ 3 x 1053 ergs # neutrinos: sum νe ~ 3.0 x 1057 νeb ~ 2.1 x 1057 νx ~ 5.2 x 1057 Following Horowitz, Coakley and McKinsey arXiv:astro-ph/0302071 v1 5 Feb 2003

  24. Neon Elastic Scattering !!! neutrino Z0 A = 20 Z=10 N=10 neon nucleus σ ~ 0.42 x 10-44 N2 (E/1 MeV)2 cm2

  25. Neon Response ObservedSpectrum Events per ton 100 ton detector  200 events @ 10 kpc

  26. Solar Neutrinos? 8B neutrinos, E >~ 10 MeV Several events/yr Er <~ 5 keV

  27. Possible 100 kg Detector

  28. R&D: WLS / CsI Studies CsI WLS + TPB

  29. R&D: Gating Circuit

  30. Key Points • Room T, Radio-quiet gas • Modular • Low threshold : 1 keV ee  3 keV NR • Signal enhancement with Xe Doping • 3-D event position • Potentially discriminating • /else still interesting for SN & Annual Mod.

  31. SUMMARY • High Pressure Neon – excellent potential for discriminating WIMP detector • Excellent leverage for Wimp Mass Determination • Good potential for HALO studies • Supernova: 100 ton -> 200 hits from SN @ 10kpc ! • And Solar neutrinos, E>~ 10 MeV

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