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

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

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

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

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

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

7. Two Big Questions!! Is a detector operating at 100 atm mechanically feasible? Is it dangerous? 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 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 ? >~ 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 ~ 40 cm spun aluminum carbon fiber winding 43 cm diameter 300 cm length 6000 psi = 408 atm

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

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

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

13. 55 Fe Spectra Light Charge

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

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

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

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

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

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

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

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

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

23. Other Applications? -Supernova E ~ 3 x 10 53 ergs ν e ~ 3.0 x 10 57 ν eb ~ 2.1 x 10 57 ν x ~ 5.2 x 10 57 ~ 10 kpc Earth # neutrinos: sum Following Horowitz, Coakley and McKinsey arXiv:astro-ph/0302071 v1 5 Feb 2003

24. Neon Elastic Scattering !!! Z0Z0 neutrino neon nucleus A = 20 Z=10 N=10 σ ~ 0.42 x 10 -44 N 2 (E/1 MeV) 2 cm 2

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

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

27. Possible 100 kg Detector

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

29. R&D: Gating Circuit

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

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