SIGN Scintillation and Ionization in Gaseous Neon A

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

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

Inelastic Response of Recoiling Nucleus Efficiency Lindhard * Threshold Effect

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

SIGN concept Cylinder n Neon Gas n n n WIMP P >= 100 atm + Xenon 0. 1 -0. 5 % *** key trick*** Cs. I Photocathode Sense & Field wires WLS fibers (optional) e. g. Diameter ~ 40 cm Length ~ 5 m Mass >~ 50 kg @ 100 atm Primary Ionization Prompt Scintillation Photoelectrons

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

Two Big Questions!! n n 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 ?

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

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

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

High Pressure Test Cell PMT Support Cell Argon Flow Charge Amp

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

55 Fe Light Charge Spectra

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

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!

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

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

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

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

If Discrimination, etc Potential Sensitivity 1 ton, 1 yr 100 tons, 1 yr

Annual Modulation Sensitivity? 1 ton neon 1 x 10 -6 pb/nucleon Bk=0. 01 evts/ke. V/kg/day Rx = ∑ 2 cos(wt) D(t) Ry = ∑ 2 sin(wt) D(t) 90% Ry Rx cosine projection method –Freese, Friedman, Gould, PRD 37 (12)(1987) 3388 -3405

WIMP sensitivity estimate Using Lindhard + Threshold Effect No Discrimination Applied

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 Mc. Kinsey ar. Xiv: astro-ph/0302071 v 1 5 Feb 2003

Neon Elastic Scattering !!! neutrino Z 0 A = 20 Z=10 N=10 neon nucleus σ ~ 0. 42 x 10 -44 N 2 (E/1 Me. V)2 cm 2

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

Solar Neutrinos? 8 B neutrinos, E >~ 10 Me. V Several events/yr Er <~ 5 ke. V

Possible 100 kg Detector

R&D: WLS / Cs. I Studies Cs. I WLS + TPB

R&D: Gating Circuit

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

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