sign: potential wimp detection using pressurized nobles
Post on 14-Jan-2016
29 Views
Preview:
DESCRIPTION
TRANSCRIPT
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
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 !
J.T. White, TAMU PPC07 May 16, 2007
Halo Dark Matter: Starting Assumption
ρ ~ 0.3 GeV/cc <v> ~ 250 km/s@ earth
WIMPs
J.T. White, TAMU PPC07 May 16, 2007
WIMP Coherent Scattering (SI)
1
A
WIMP
E_recoil
20 Ascalar
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
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!
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
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
J.T. White, TAMU PPC07 May 16, 2007
4-PMT - 100 atm
4-PMT Test Cell
PTFE reflector
Field tube
J.T. White, TAMU PPC07 May 16, 2007
Sapphire Windows
TPB coating
J.T. White, TAMU PPC07 May 16, 2007
Field Tuning
Adjust field tube potentialto optimize E-field uniformityalong sense wire
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)
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
J.T. White, TAMU PPC07 May 16, 2007
Calibration
122 keV Gamma
92 keV e-
30 keV x-ray
unobserved
J.T. White, TAMU PPC07 May 16, 2007
Calibration
122 keV Gamma
92 keV e-
30 keV x-ray
unobserved
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
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 ***
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
J.T. White, TAMU PPC07 May 16, 2007
Results
Xe @ 20 atm~ 300 psi
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
J.T. White, TAMU PPC07 May 16, 2007
Xe – 20 atm Nuclear Recoil response
S2/S1
Er_max ~ 27 keV
gammas
neutrons
J.T. White, TAMU PPC07 May 16, 2007
S2 Spectra
Co-57 data
?
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%
J.T. White, TAMU PPC07 May 16, 2007
Xe – S2/S1 Discrimination
23.7 116
Centroid Separation > X4
21.6 107
J.T. White, TAMU PPC07 May 16, 2007
Results
ArXe(0.5%) @ 50 atm~ 750 psi
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
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…)
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!
J.T. White, TAMU PPC07 May 16, 2007
Results
NeXe(0.5%) @ 100 atm
1600 psi
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)
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
J.T. White, TAMU PPC07 May 16, 2007
Primary Pulse Shape Discrimination
J.T. White, TAMU PPC07 May 16, 2007
S2/S1 AND Primary ShapeDiscrimination!
Primary Pulse Shape Discrimination
Gammas
Neutrons
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
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
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
J.T. White, TAMU PPC07 May 16, 2007
Detector Concept
Composite Cylinder Hub w/ WLS Fiber structure
J.T. White, TAMU PPC07 May 16, 2007
Drift Flow
SteeringElectrodes
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.
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
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 !
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
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
top related