SIGN Scintillation and Ionization in Gaseous Neon A

SIGN (Scintillation and Ionization in Gaseous Neon) A High-Pressure, Room-Temperature, Gaseous-Neon. Based Underground Physics Detector J. T. White Texas A&M University Institutions: TAMU, UCLA SNOLAB workshop V Aug, 22 2006

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

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

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

Potential WIMP Sensitivity? IF Threshold ~ 1 ke. V 1 ton Few 10 -46 cm 2 ?

Solar Neutrinos? 8 Be: Flux ~106/cm 2/s E > 10 Me. V Coherent Nuclear Scattering: Drukier, Stodolsky, PRD 30 (11) (1984) 2295 -2309 Cabrera, Krauss, Wilczek, PRL 55(1) (1985)25 -28 σ ~ 0. 42 x 10 -44 N 2 (E/1 Me. V)2 cm 2 Er_MAX = (2/A) (Eν 2/1 Me. V)2 ke. V ~ 10 ke. V for Ev = 10 Me. V <Er> = Er_MAX/3 ke. V ~ ~ 15 evts/year/ton Er: 3 10 Ke. V

Neutrinos –Supernova? Earth ~ 10 kpc E ~ 3 x 1053 ergs # neutrinos: sum νe ~ 3. 0 x 1057 νebar ~ 2. 1 x 1057 νx ~ 5. 2 x 1057 Horowitz, Coakley, Mc. Kinsey, PRD 68 023005 (2003)

Neon Coherent Elastic Scattering neutrino A = 20 Z=10 N=10 ~2. 5 evts/ton Flavor Indep! σ ~ 0. 42 x 10 -44 N 2 (E/1 Me. V)2 cm 2

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

55 Fe Signal in Ne/Xe(0. 5%) Primary S 2 Light ~2 us Photoelectric from SS QE ~. 02% @175 nm ? Secondary Charge charge preamp signal - note kink

55 Fe Light Charge 6 ke. V gamma in Ne-Xe(0. 5%)

Another Example: 241 Am gammas 60 ke. V Charge Signal Excellent Resolution !

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

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

Sapphire Windows TPB coating

Event Waveforms Neutron Event Gamma Event Primary (S 1) Secondary (S 2) Areas Same i. e. ionization same

S 2 pulse width Multiple scatters, photoelectric x -rays & higher energy gammas Low energy gammas and neutrons Width increase vs drift time Can determine diffusion coeff.

Nuclear Recoil Discrimination: S 2 vs S 1 Am. Be Neutron Source n i m zoo 100 atm Ne/Xe(0. 5%)

Nuclear Recoil Discrimination: S 2 vs S 1 Drift regions Higher field Lower field S 2/S 1 field (and density) dependent for nuclear recoils Gammas unaffected (Emin ~ 600 v/cm here)

S 2 / S 1 S 2/S 1 Discrimination Gammas Neutrons vs S 1 vs S 2

Primary Pulse Shape Discrimination

S 2/S 1 AND Primary Shape Discrimination! Primary Pulse Shape Discrimination Gammas Neutrons

S 2/S 1 AND Primary Shape Discrimination! Primary Pulse Shape Discrimination Gammas Neutrons

Gas Mixture Studies ZERO Field Gammas Neutrons 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 Cylinder n n WIMP Neon + ? Gas Cs. I Photocathode Sense & Field wires WLS fibers e. g. Diameter ~ 50 cm Length ~ 5 m Mass >~ 100 kg @ 100 atm Primary Ionization Prompt Scintillation Photoelectrons

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 43 cm diameter 300 cm length 6000 psi = 408 atm ~ 40 cm spun aluminum carbon fiber winding

SIGN Conceptual Design Mg. F 2 - coated LEXAN light guide PMT Both Ends WLS Fibers Coated With TPB Charge Readout -Both Ends -Can sum wires

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

Possible 100 Ton Detector

WIMP sensitivity - Oscillation Future: WIMP velocity dispersion measurement

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

Summary n n n 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 S 2/S 1 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?