J.T. WhiteJ.T. White

Texas A&M UniversityTexas A&M University

SIGN(Scintillation and Ionization in Gaseous Neon)

A WIMP Detector based on Gaseous Neon

The Future of Dark Matter DetectionUniversity of Chicago, Dec. 9-10, 2004

Institutions:TAMU, UCLA

WIMP – Neon InteractionWIMP – Neon InteractionWIMP

Ne

NuclearRecoil

F(Q2) ~ 1

1 ton, 1.e -8 pb/n

Inelastic Response of Recoiling Inelastic Response of Recoiling NucleusNucleus

Lindhard

Lindhard * Threshold Effect

Efficiency

Observable SpectraObservable Spectra

Recoil Spectra IF ~ALL Lindhard Energy is observed with 100% efficiency.

1 ton, 1.e - 8 pb/nucleon

SIGNSIGN concept concept

Neon Gas Neon Gas P >= 100 atmP >= 100 atm + Xenon 0.1-0.5 %+ Xenon 0.1-0.5 % *** key trick****** key trick***

CsI PhotocathodeCsI Photocathode Sense & Field wiresSense & Field wires WLS fibers (optional)WLS fibers (optional)e.g.Diameter ~ 40 cmLength ~ 5 mMass >~ 50kg @ 100 atm

WIMP

Primary IonizationPrompt Scintillation

Photoelectrons

Cylinder

Effect of Effect of Xenon doping !!!Xenon doping !!!

Ne* + Ne → Ne2* → 2Ne + 80 nm80 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

3/21/2

3/21/2

Note ! Nuclear Recoils: mostly Ne*(?), Electron: mostly Ne+

or

(in a few microns)

Ne+ + Xe → Ne+Xe → NeXe+ + 134nm

→ and some Ne*

then

or

Two Big Questions!!Two Big Questions!!

Is a detector operating at 100 atm Is a detector operating at 100 atm mechanically feasible?mechanically feasible? Is it dangerous?Is it dangerous?

Is it possible to operate a proportional Is it possible to operate a proportional counter with P >~ 100 atm ?counter with P >~ 100 atm ? Usually wire Usually wire chambers operate at >~ 1000 V – does chambers operate at >~ 1000 V – does this mean one would have to operate this mean one would have to operate

>~ 100,000 V>~ 100,000 V ? ?

Safety?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 ModuleOff-the-shelf Module

~ 3 m

~ 40 cm

spun aluminum

carbon fiberwinding

43 cm diameter 300 cm length6000 psi = 408 atm

Signal at P > 100 atm?Signal at P > 100 atm?

Test Cell

PMT

Charge Amp Radioactivesource

+HV- HV

Sapphire

100 atm NeXe(.5%)ElectrofluorescenceMostly 175 nm

High Pressure Test CellHigh Pressure Test Cell

Charge Amp

PMT Support

Cell

Argon Flow

5555Fe SignalFe Signal

Primary

Secondary

Photoelectric from SSQE ~ .02% @175 nm

charge preamp signal- note kink

Light

Charge

~2 us

5555Fe SpectraFe SpectraLight

Charge

241241Am AlphaAm Alpha

Light

ChargeShaping Amp1 us shaping

Primary Secondary

Answers to Two Big Answers to Two Big QuestionsQuestions

1) Yes, safe enough for the public!1) Yes, safe enough for the public!

2) Yes, at V ~ 5000 V, tube diameter ½ 2) Yes, at V ~ 5000 V, tube diameter ½ in,in,

125 um sense wire 125 um sense wire

- Charge gain ~~ 300 (preliminary) - Charge gain ~~ 300 (preliminary)

- Light Gain ~~ 2000 photons/e- Light Gain ~~ 2000 photons/e- -

(preliminary) at 175 nm!(preliminary) at 175 nm!

SignalSignal

Primary Ionization

ScintillationFrom CsI

Feedback of ionization signal from CsI – perhaps saturated.

Feedback of Scintillationsignal from CsI – amplified!

Max Drift timeGating Pulse

Drift Field and GatingDrift Field and GatingEqui-potentials Drift Trajectories

CAN Gate Field Wires Between Sense Wires – few KV !

SIGNSIGN Conceptual DesignConceptual Design

PMTBoth Ends

Charge Readout -Both Ends -Can sum wires

MgF2- coatedLEXAN light guide

WLS FibersCoated With TPB

Structure of Inner CylinderStructure of Inner Cylinder

Blue-Green WLS Fiber

TPBVUV toblue

Sense wire

Stainless Steel Inner CylinderHollow, Stiff

Field/Gating Wires

If Discrimination, etc If Discrimination, etc Potential SensitivityPotential Sensitivity

1 ton, 1 yr 100 tons, 1 yr

Annual Modulation Annual Modulation Sensitivity?Sensitivity?

Rx = ∑ 2 cos(wt) D(t)Ry = ∑ 2 sin(wt) D(t)

RxRy

cosine projection method –Freese, Friedman, Gould, PRD 37 (12)(1987) 3388-3405

90%

1 ton neon1 x 10-6 pb/nucleonBk=0.01evts/keV/kg/day

WIMP sensitivity estimateWIMP sensitivity estimateUsing Lindhard + Threshold Effect

No Discrimination Applied

Other Applications? -Other Applications? -SupernovaSupernova

E ~ 3 x 1053 ergs

νe ~ 3.0 x 1057

νeb ~ 2.1 x 1057

νx ~ 5.2 x 1057

~ 10 kpcEarth

# neutrinos:sum

Following Horowitz,Coakley and McKinseyarXiv:astro-ph/0302071 v15 Feb 2003

Neon Neon ElasticElastic Scattering Scattering !!!!!!

Z0

neutrino

neon nucleus

A = 20Z=10N=10

σ ~ 0.42 x 10-44 N2 (E/1 MeV)2 cm2

Neon ResponseNeon Response

Observed Spectrum

Events per ton

100 ton detector 200 events @ 10 kpc

Solar Neutrinos?Solar Neutrinos?

8B neutrinos, E >~ 10 MeV

Several events/yr Er <~ 5 keV

Possible 100 kg DetectorPossible 100 kg Detector

R&D: WLS / CsI StudiesR&D: WLS / CsI Studies

WLS + TPB

CsI

R&D: Gating CircuitR&D: Gating Circuit

Key PointsKey Points

Room T, Radio-quiet gasRoom T, Radio-quiet gas ModularModular Low threshold : 1 keV ee Low threshold : 1 keV ee 3 keV NR 3 keV NR Signal enhancement with Xe DopingSignal enhancement with Xe Doping 3-D event position3-D event position Potentially discriminatingPotentially discriminating /else still interesting for SN & Annual /else still interesting for SN & Annual

Mod.Mod.

SUMMARYSUMMARY

High Pressure Neon – excellent potential High Pressure Neon – excellent potential for discriminating WIMP detectorfor discriminating WIMP detector

Excellent leverage for Excellent leverage for WWimp imp MMass ass DDeterminationetermination

Good potential for HALO studiesGood potential for HALO studies Supernova: 100 ton -> 200 hits from SN Supernova: 100 ton -> 200 hits from SN

@ 10kpc ! @ 10kpc ! And Solar neutrinos, E>~ 10 MeVAnd Solar neutrinos, E>~ 10 MeV