sign: potential wimp detection using pressurized nobles
DESCRIPTION
SIGN: Potential WIMP Detection using Pressurized Nobles. J.T. White Texas A&M University 5/16/07. Why Gaseous Nobles?. Original Motivation: Neon Electron mobility possible S2/S1 discrimination fiducial well defined Also: Room temperature operation Simpler purification - PowerPoint PPT PresentationTRANSCRIPT
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J.T. White, TAMU PPC07 May 16, 2007
SIGN:Potential WIMP Detection using
Pressurized Nobles
J.T. White
Texas A&M University
5/16/07
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J.T. White, TAMU PPC07 May 16, 2007
Why Gaseous Nobles?
• Original Motivation:– Neon
• Electron mobility possible S2/S1 discrimination fiducial well defined
• Also:– Room temperature operation
• Simpler purification• No leveling• No Cryo, etc …
• NEW!!– S2/S1 Discrimination observed !
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J.T. White, TAMU PPC07 May 16, 2007
Halo Dark Matter: Starting Assumption
ρ ~ 0.3 GeV/cc <v> ~ 250 km/s@ earth
WIMPs
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J.T. White, TAMU PPC07 May 16, 2007
WIMP Coherent Scattering (SI)
1
A
WIMP
E_recoil
20 Ascalar
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J.T. White, TAMU PPC07 May 16, 2007
A2 Dependence of Recoil Spectra
0
min
0
min22
00 )(4 v
vverf
v
vverfEF
mmvdE
dR ee
RrxeR
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J.T. White, TAMU PPC07 May 16, 2007
But, World is Radioactive!Gamma, beta
Electron recoil
U, Th, 40K, cosmogenics,etc, etc. . . .
Nuclear / Electron recoil Discrimination Very important!
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J.T. White, TAMU PPC07 May 16, 2007
S2/S1 discrimination in nobles
Gammabackground
electronrecoil
Target Nuclei
nuclear recoil
WIMP orNeutron
Scintillation
Ionization
Background Discrimination
S2
S1
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J.T. White, TAMU PPC07 May 16, 2007
Pressurized noble gasTest Cell
12.7 mm
12.7 mm
8 mm
Primary ScintillationS1
Prop. ScintillationS2
S1 S2
PTFESapphire Windows
Field Tube
Sense Wire
TPB
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J.T. White, TAMU PPC07 May 16, 2007
4-PMT - 100 atm
4-PMT Test Cell
PTFE reflector
Field tube
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J.T. White, TAMU PPC07 May 16, 2007
Sapphire Windows
TPB coating
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J.T. White, TAMU PPC07 May 16, 2007
Field Tuning
Adjust field tube potentialto optimize E-field uniformityalong sense wire
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J.T. White, TAMU PPC07 May 16, 2007
Event Waveforms (Ne-Xe example)
Neutron EventGamma Event
Areas Samei.e. ionization same
Secondary(S2)
Primary(S1)
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J.T. White, TAMU PPC07 May 16, 2007
Calibration
122 keV Gamma (+ some 136)
92 keV e-
30 keV x-ray
12.7 mm
12.7 mm
8 mmRange 92 keV e- ~ 2 mm
Xe gas: 20 atm
Range 30 keV e- ~ 0.2 mm
Range 30 keV x-ray ~ 1 cm
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J.T. White, TAMU PPC07 May 16, 2007
Calibration
122 keV Gamma
92 keV e-
30 keV x-ray
unobserved
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J.T. White, TAMU PPC07 May 16, 2007
Calibration
122 keV Gamma
92 keV e-
30 keV x-ray
unobserved
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J.T. White, TAMU PPC07 May 16, 2007
Calibration
122 keV Gamma
92 keV e-
30 keV x-ray
Leff ~ 4.5% if Ws=76ev/phQgain ~ 1.2 p.e./e- (here)
unobserved
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J.T. White, TAMU PPC07 May 16, 2007
Neutron Scatteringw/ Mono-Energetic Neutrons
θ
Er, M
En, m
En’
Θ π
Er Ermax = (4 m M/(m+M)2) En
S – Wave
Er
dN/dErCM frame
Edge ***
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J.T. White, TAMU PPC07 May 16, 2007
4-MeV Proton Acceleratorat TAMU
Monochromatic neutrons up to 2 MeVusing 7(Li(p,n)7Be reactions.
Tandem van de Graaff
DuoplasmatronIon sourceup to ~ 15 uA
Achieved>1 uA on target >5E6 n/sr/s
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J.T. White, TAMU PPC07 May 16, 2007
Results
Xe @ 20 atm~ 300 psi
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J.T. White, TAMU PPC07 May 16, 2007
Digression: Two-Phase Xenon Discrimination
Gammas
Neutrons
Centroid Separation ~ x 2
Recoil Energy (KeVr)
S2/S1
Acceptance box
See Tom Shutt’s talk tomorrow !!
TAMU Test CellAmBe Source
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J.T. White, TAMU PPC07 May 16, 2007
Xe – 20 atm Nuclear Recoil response
S2/S1
Er_max ~ 27 keV
gammas
neutrons
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J.T. White, TAMU PPC07 May 16, 2007
S2 Spectra
Co-57 data
?
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J.T. White, TAMU PPC07 May 16, 2007
Xe – 20 atm NR Q & L yields
39 keV
27 keV Assuming Wi = 21.7 ev/e-
Assuming Leff=4.5%
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J.T. White, TAMU PPC07 May 16, 2007
Xe – S2/S1 Discrimination
23.7 116
Centroid Separation > X4
21.6 107
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J.T. White, TAMU PPC07 May 16, 2007
Results
ArXe(0.5%) @ 50 atm~ 750 psi
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J.T. White, TAMU PPC07 May 16, 2007
ArXe(0.5%) – 50 atmNR Response
Er_max ~ 104 keV
~ 15 events/ton/yr @ 10-45 pb/nEr threshold 40 keVr, Mx=100 GeV
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J.T. White, TAMU PPC07 May 16, 2007
Ar Xe(0.5%) – Charge Yield
120 keV
85 keV Average overE ~ 0.6 2.5 kV/cm
Key! (Penning effect…)
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J.T. White, TAMU PPC07 May 16, 2007
ArXe(0.5%) – Light Yield
E ~ 0.6 2.5 kV/cm E ~ 0.6 2.5 kV/cm
Key!
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J.T. White, TAMU PPC07 May 16, 2007
Results
NeXe(0.5%) @ 100 atm
1600 psi
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J.T. White, TAMU PPC07 May 16, 2007
Event Waveforms (Ne-Xe example)
Neutron EventGamma Event
Areas Samei.e. ionization same
Secondary(S2)
Primary(S1)
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J.T. White, TAMU PPC07 May 16, 2007
Nuclear Recoil Discrimination: S2 vs S1
Drift regions
Higher field
S2/S1 field (and density) dependent for nuclear recoilsGammas unaffected (Emin ~ 600 v/cm here)
Lower field
AmBe
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J.T. White, TAMU PPC07 May 16, 2007
Primary Pulse Shape Discrimination
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J.T. White, TAMU PPC07 May 16, 2007
S2/S1 AND Primary ShapeDiscrimination!
Primary Pulse Shape Discrimination
Gammas
Neutrons
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J.T. White, TAMU PPC07 May 16, 2007
NeXe(0.5%) – 100 atmNR Response
Er_max ~ 140 keV
Red = 140 keVrBased on S2
~ 1.8 evts/ton/yr @ 10-45 pb/n@ Er >= 40 keV Mx=100 GeV
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J.T. White, TAMU PPC07 May 16, 2007
NeXe(0.5%) – Q&L Yield
E ~ 0.6 2 kV/cmE ~ 0.6 2 kV/cm
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J.T. White, TAMU PPC07 May 16, 2007
SIGN conceptual design
• Gas• CsI Photocathode• Light gain structure using WLS fibers
WIMP
Primary IonizationPrompt Scintillation
Photoelectrons
Cylinder
S2 S1
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J.T. White, TAMU PPC07 May 16, 2007
Detector Concept
Composite Cylinder Hub w/ WLS Fiber structure
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J.T. White, TAMU PPC07 May 16, 2007
Drift Flow
SteeringElectrodes
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J.T. White, TAMU PPC07 May 16, 2007
Gas Light Multiplier ConceptCirlex metallized plate, ~ 1mm holes
VUV synthetic silica plates
Platinum coating – VUV transmitting
VUV -> blue phosphor coating
WLS Fibers
100% e- transmissionFluorescence E/P>1Lit – 0.006 p.e./vuv pho.
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J.T. White, TAMU PPC07 May 16, 2007
100 kg 20 atm Xe Prototype
3 m
0.6 m
Shielding
CsI
PMT
SS Tube~0.25 inch wall WLS Fibers
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J.T. White, TAMU PPC07 May 16, 2007
FutureComposite Vessels
•Carbon, Kevlar wound•Some rated > 10000 psi !•Used on mass transit (Methane))•Used for Hydrogen fuel cells•On jets, spacecraft•DOT certified !
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J.T. White, TAMU PPC07 May 16, 2007
Shielding
10 modules 1 ton
~~4-5 m
4 m watershield
See LUX discussionIn Tom Shutt’s talk
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J.T. White, TAMU PPC07 May 16, 2007
Plans – Phased Program
• 100 kg Xe proto-experiment– Water shield– SS vessel– Only 300 psi …
• Future – Neon @ 200 atm– WIMP Mass = ????– Halo velocity dispersion = ????– Number of “species” = ????
Even a caveman could do it
Xenon
Neon