# J.T. White Texas A&M University SIGN (Scintillation and Ionization in Gaseous Neon) A High-Pressure, Room- Temperature, Gaseous-Neon-Based Underground.

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J.T. White Texas A&M University SIGN (Scintillation and Ionization in Gaseous Neon) A High-Pressure, Room- Temperature, Gaseous-Neon-Based Underground Physics Detector DMSAG Los Angeles, Ca. Aug, 15 2006 Institutions: TAMU, UCLA

High Pressure Gaseous Neon? High Pressure Gaseous Neon?  Electron mobility !  ~ 8  25% liquid density 2) What Pressure? 1) Why Gaseous Neon?  ~100  300 atms !  Possibility for Primary vs Secondary Nuclear Recoil Discrimination 3) What Temperature?  Room T !

WIMP Physics with NEON ? WIMP Er σ/atom  A 2  cost/reach similar to Xe Sensitivity Relative to Xe? σ/kg  A cost/kg < 1/10 Xe Rate/kg: Ne/Xe ~ A Ne /A Xe ~ 1 / 6.5

Also Form Factor  Relative Rate/kg > A Ne /A Xe

WIMP – Recoil Spectrum Complimentary to Xe, Ge, Ar Slope strongly dependent on WIMP mass & velocity dispersion(?)

Visible Energy? Visible Energy? Lindhard Lindhard * Threshold Effect Inelastic Efficiency Recoil Energy Lindhard Visible Energy (e.e.)

Potential WIMP Sensitivity? 1 ton  Few 10 -46 cm 2 ? IF Threshold ~ 1 keV

Solar Neutrinos? Er_MAX = (2/A) (E ν 2 /1 MeV) 2 keV ~ 10 keV for Ev = 10 MeV 8 Be: Flux ~10 6 /cm 2 /s E > 10 MeV Coherent Nuclear Scattering:  ~ ~ 15 evts/year/ton Er: 3  10 KeV σ ~ 0.42 x 10 -44 N 2 (E/1 MeV) 2 cm 2 = Er_MAX/3 keV Drukier, Stodolsky, PRD 30 (11) (1984) 2295-2309 Cabrera, Krauss, Wilczek, PRL 55(1) (1985)25-28

Neutrinos –Supernova? E ~ 3 x 10 53 ergs ν e ~ 3.0 x 10 57 ν ebar ~ 2.1 x 10 57 ν x ~ 5.2 x 10 57 ~ 10 kpc Earth # neutrinos: sum Horowitz, Coakley, McKinsey, PRD 68 023005 (2003)

Neon Coherent Elastic Scattering neutrino A = 20 Z=10 N=10 σ ~ 0.42 x 10 -44 N 2 (E/1 MeV) 2 cm 2 ~2.5 evts/ton Flavor Indep!

SIGNAL in HP-Ne? 100 atm Test Cell PMT Radioactive source +HV - HV Sapphire 100 atm NeXe Electrofluorescence Mostly 175 nm PMT Cell Argon Flow Charge Amp

Example: Neon doped with Xenon Ne* + Ne  Ne*Ne  2Ne + 90 nm 90 nm + Xe  Xe + + e - Ne* + Xe  Ne*Xe  NeXe + + e - Ne + + Xe  Ne+Xe  NeXe + + 134nm Some Xe + + e- -> Xe* and some Xe* directly produced Xe* + Xe  Xe*Xe  2Xe + 175 nm Interaction -> Ne* and Ne + + e - then 90 nm travels < 1 um,.5%Xe 3/2 1/2 3/2 1/2 Nuclear Recoils: mostly Ne* Electron Recoils: mostly Ne + ~100% Ne* -> Ionization ? Ne + - > 134 nm ? Ne* Ne +

55 Fe Signal in Ne/Xe(0.5%) Primary Secondary Photoelectric from SS QE ~.02% @175 nm ? charge preamp signal - note kink S2 Light Charge ~2 us

55 Fe 6 keV gamma in Ne-Xe(0.5%) Light Charge 6 keV

Another Example:  Excellent Resolution ! 241 Am gammas 60 keV Charge Signal

Nuclear Recoil Discrimination? 4-PMT 100 atm Test Cell 4-PMT Test Cell PTFE reflector Field tube

Field Tuning Field Tuning Adjust field tube potential to optimize E-field uniformity along sense wire

Sapphire Windows TPB coating

Event Waveforms Neutron Event Gamma Event Areas Same i.e. ionization same Secondary (S2) Primary (S1)

Electron Mobility V drift = dr/dt = μ(E) E Uniform illumination: N = N T πr 2 l dN/dr = dN/dt / dr/dt dN/dt = N T 2πrl V drift μ(E) = N T 2 π rl dN/dt/E  Can determine μ(E)

S2 pulse width Low energy gammas and neutrons Multiple scatters, photoelectric x-rays & higher energy gammas Width increase vs drift time  Can determine diffusion coeff.

Nuclear Recoil Discrimination: S2 vs S1 AmBe Neutron Source 100 atm Ne/Xe(0.5%) zoom in

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

S2/S1 Discrimination Gammas Neutrons vs S2vs S1 S2 / S1

Primary Pulse Shape Discrimination

S2/S1 AND Primary Shape Discrimination! Primary Pulse Shape Discrimination Gammas Neutrons

S2/S1 AND Primary Shape Discrimination! Primary Pulse Shape Discrimination Gammas Neutrons

Other gases? Example: Pure Neon Gammas Neutrons ZERO Field

Gas Mixture Studies: Pure Neon ZERO Field Neutrons Gammas Point sampling: pure Ne  Ne-Xe  Ne-Ar  Ne-He mixures all show discrimination. L/Q output, primary decay times vary with mixtures. Need full study.

SIGN conceptual design Neon + ? Gas CsI Photocathode Sense & Field wires WLS fibers e.g. Diameter ~ 50 cm Length ~ 5 m Mass >~ 100kg @ 100 atm WIMP Primary Ionization Prompt Scintillation Photoelectrons Cylinder

Pressure Vessel? 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

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

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

Structure of Inner Cylinder Blue-Green WLS Fiber TPB VUV to blue Sense wire Inner Cylinder Field/Gating Wires

Drift Field and Gating CsI Gate with field wires Or with outer grid Drift Trajectories

Detector Layout 1 ton @ 100 bars 10 tons 5 m 9 m 2- 4 m water/acrylic shields

Possible 100 Ton Detector

WIMP sensitivity - Oscillation Future: WIMP velocity dispersion measurement

What we know Signal characteristics: Q and L gain vs E & P Q and L gain vs E & P Drift characteristics: e mobility & diffusion e mobility & diffusion Obs. Discrimination: S2/S1 AND S1 shape S2/S1 AND S1 shape Pressure vessel: fiber composite fiber compositeReadout: Q L or both? Q L or both? 3-d position info 3-d position info Absolute Q & L yield Gas mix optimization Readout development WLS Fibers / Charge CsI coating & gating Material Screening Fibers, bonder, linerShielding H2O?, Acrylic? Plastic? Part of pressure vessel? What we need

Nuclear Recoil Calibration and Signal Efficiency Determination: Li(p,n)Be reaction  ~ monochromatic neutrons with Energies up to ~ 2 MeV  Beam commissioning in progress TAMU Proton Accelerator – 4 MeV max

Cost Drivers: Detector Components Neon - \$80k/ton 100 kg module - \$25k Pressure vessel \$5k Pressure vessel \$5k Internal hub / wiring / WLS structure : \$5k Internal hub / wiring / WLS structure : \$5k Readout: Readout: 2 pmts/vessel, 2 wfd chan. \$5k Charge readout both ends + dig channels \$5k Steel storage vessel + plumbing \$5k Steel storage vessel + plumbing \$5k High pressure diaphragm pump for storage transfer and circulation ~ \$50k - (1 per ton)  1 ton detector <~ \$500k

Cost Drivers: Personnel Post-doc: \$80k/yr 2 grad students: \$80k/yr 2 undergrads: \$20k/yr PI – sum. Sal.: \$40k/yr Travel: \$20k/yr Misc: \$10k/yr Estimated costs including salaries + overhead + fringe  5 institutions ~ 1.25 \$M/yr

Cost Drivers: R&D and Engineering of Detector Engineering: Pressure vessel/internals ~ \$100k Pressure vessel/internals ~ \$100k R&D – 2 year program: Personnel – 5 inst * 2 years \$2.5 M Personnel – 5 inst * 2 years \$2.5 M Components: (prototypes+pump+gases+PMTs etc) Components: (prototypes+pump+gases+PMTs etc) ~\$0.5M ~\$0.5M Accelerator operation/calib work ~ \$100k  Development of detector over 2 years ~ \$3.2M

Cost Drivers: Shielding and Underground Lab Shielding: 2-4 m H2O or acrylic: \$??? 10 X 10 X 10 m room for detector: \$??? Room for gas storage/counting room: \$???  No estimate yet

Cost Drivers: Summary Neon: \$80k/ton Detector modules: 10 X \$25k = \$250k/ton Gas Pumping: \$50k/ton Personnel (5 inst): \$1.25M/yr R&D/Engineering/final design: \$3.2M 2yrs Shielding / Excavation / ug Lab: \$??? Operating cost: room T, gas circ: Small compared to cryogenic detectors Measurement of WIMP properties: Priceless

Summary Room-Temperature, High-Pressure, Gaseous Neon (or Ne+?) is proposed as a dark matter/ neutrino Target It is radio-quiet! Shows excellent (potential) NR Discrimination in BOTH S2/S1 and Primary Pulse Shape ! Relatively inexpensive Will be important in the future to help pin down WIMP mass & velocity distribution? May be able to detect SN, 8 B, Geo-Fission(?) neutrinos – flavor independent?

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