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

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 !

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

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

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

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!

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

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

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

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

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

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)

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

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

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

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

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 ***

J.T. White, TAMUPPC07 May 16, 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

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

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

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

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

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%

J.T. White, TAMUPPC07 May 16, 2007 Xe – S2/S1 Discrimination Centroid Separation > X

J.T. White, TAMUPPC07 May 16, 2007 Results 50 atm ~ 750 psi

J.T. White, TAMUPPC07 May 16, 2007 ArXe(0.5%) – 50 atm NR Response Er_max ~ 104 keV ~ pb/n Er threshold 40 keVr, Mx=100 GeV

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…)

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

J.T. White, TAMUPPC07 May 16, 2007 Results 100 atm 1600 psi

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)

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

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

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

J.T. White, TAMUPPC07 May 16, 2007 NeXe(0.5%) – 100 atm NR Response Er_max ~ 140 keV Red = 140 keVr Based on S2 ~ Er >= 40 keV Mx=100 GeV

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

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

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

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

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 – p.e./vuv pho.

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

J.T. White, TAMUPPC07 May 16, 2007 Future  Composite Vessels Carbon, Kevlar wound Some rated > psi ! Used on mass transit (Methane)) Used for Hydrogen fuel cells On jets, spacecraft DOT certified !

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

J.T. White, TAMUPPC07 May 16, 2007 Plans – Phased Program 100 kg Xe proto-experiment –Water shield –SS vessel –Only 300 psi … Future – 200 atm –WIMP Mass = ???? –Halo velocity dispersion = ???? –Number of “species” = ???? Even a caveman could do it Xenon Neon