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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
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
5555Fe SignalFe Signal
Primary
Secondary
Photoelectric from SSQE ~ .02% @175 nm
charge preamp signal- note kink
Light
Charge
~2 us
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
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