Applications of Micro-TPC to Dark Matter Search 1. WIMP signatures 2. Performance of the Micro-TPC...
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Transcript of Applications of Micro-TPC to Dark Matter Search 1. WIMP signatures 2. Performance of the Micro-TPC...
Applications of Micro-TPCApplications of Micro-TPCtoto
Dark Matter SearchDark Matter Search
1. WIMP signatures1. WIMP signatures
2. Performance of the Micro-TPC2. Performance of the Micro-TPC
3. WIMP-wind measurement3. WIMP-wind measurement
4. Future works4. Future works
5. Conclusions5. Conclusions
Jun. 13, 2003Jun. 13, 2003
Atsushi TakedaAtsushi Takeda for the μ-PIC groupfor the μ-PIC group
1. WIMP signatures1. WIMP signatures
Annual modulationAnnual modulation
Very hard Very hard to see… to see…
Movement of the earth Movement of the earth
Expected spectraExpected spectra
rate difference is a few %
BGs themselves are likely to have it
based on the motion of the earth around the sun
WIMP-windWIMP-wind
Strongly peaked in
the Cygnus direction
WIMP-wind
WIMP-wind
WIMP-wind
blowing from the direction of the solar motion
A directional sensitivedetector is needed
WIMP-wind distributionWIMP-wind distribution
180 -180
-90
90
2. Performance of the Micro-TPC2. Performance of the Micro-TPC
Micro Pixel Chamber (μ-PIC)Micro Pixel Chamber (μ-PIC)
Micro-TPCMicro-TPC μ-PIC: X, Y TPC: Z (drift time)
3D trackingSchematic structure of the μ-PIC
Micro-TPC = μ-PIC + TPC
Micro pattern gas detector Fine position resolution
(400 μm pitch) 2D imaging
10×10cm2
Pictures of the Micro-TPCPictures of the Micro-TPC
10×10cm2 μ-PIC
readoutTPC
TPC gas package
10×10×8cm3 Micro-TPChas been developed
3D Tracking performance3D Tracking performance
track length > 5 mm (several points, direction)
ProtonProton tracks tracks
neutron
dE/dx (Brag curves)dE/dx (Brag curves)
neutron
Ar : C2H6 = 9 : 1 (1 atm)
252252Cf run (n+γ)Cf run (n+γ)
dE/dx [keV/cm] 5000
χ2 /
d.o
.f30
0
neutron0
0
2222Na run (γ)Na run (γ)
dE/dx [keV/cm] 500
χ2 /
d.o
.f30
γ-rayγ-ray discriminationdiscrimination
χ2 vs dE/dx plotvs dE/dx plot
neutron events have
large dE/dxstraight track
neutron( 14 / 500 events )
>95% γ-rays were >95% γ-rays were discriminated discriminated
n efficiency ~ 1n efficiency ~ 1
(511 keV γ)
3. WIMP-wind measurement 3. WIMP-wind measurement with Micro-TPC with Micro-TPC
MeritMeritrecoil track and directionrecoil track and direction
γ-ray discriminationγ-ray discrimination
fine pitch (400μm) ⇔ DRIFT(2mm)fine pitch (400μm) ⇔ DRIFT(2mm)
Mass productionMass production
DemeritDemeritlow mass (gas detector)low mass (gas detector)
Target gasTarget gas Spin-dependent (SD): CF4, Xe Spin-independent (SI): Xe
Gas pressure, target massGas pressure, target mass threshold: 40 keV track: 5 mm
gasgas PressurePressure[Torr][Torr]
DensityDensity
[g/m[g/m33]]
dE/dxdE/dx[keV/cm][keV/cm]
CFCF44 2020 9090 8585
Xe Xe 55 3838 120120
(μ- PIC threshold : 50keV/cm)(μ- PIC threshold : 50keV/cm)
OK
pressurepressure
~ 10×1m~ 10×1m33 detector is detector is neededneeded
~ 10×1m~ 10×1m33 detector detector prototype : 30×30×30cmprototype : 30×30×30cm33
large area μ-PIC : 50×50×50cmlarge area μ-PIC : 50×50×50cm33
×8 = 1m×8 = 1m33
1m1m33×10×10
μ-PICdrift plane
×8electronics
1 m3 volume
×10 modules
50cm
50cm50cm50cm50cm
modularize
modularize
spectrum spectrum
threshold threshold
forward/backward forward/backward >10>10
Expected signalsExpected signals
for SD interactionfor SD interaction
gas: CF4
WIMP-p: 0.1 pb
recoil asymmetry recoil asymmetry
forwardbackward
WIMPWIMP WIND WIND
γγ
FF
800800
2020240240
800800
1040104082082011-1-1 00
cos γcos γ
more than 5σmore than 5σasymmetryasymmetry
CFCF44 detection possibility detection possibility Backgrounds: fast neutron 2×102×10-5cmcm-2ss-1@Kamioka@Kamioka
⇒ ⇒ 0.1 cpd/kg/keV0.1 cpd/kg/keV for CF4 (10cm water shield)for CF4 (10cm water shield)
⇒ ⇒ 16001600 BG events / 10mBG events / 10m3×1yr×1yr
WIMPs: 260 events / 10m/ 10m3×1yr×1yr
Estimated detection possibilityEstimated detection possibility
5σ 2σ
SI SD
Xe 10 m3, 1 yearnoshield
5σ
5σ
Xe 30 m3, 3 years35cm water shield
CF4 10 m3, 1 yearnoshield
CF4 30 m3, 3 years35cm water shield
5σ
5σ
2σ
2σ
2σ
2σ
4. Future works4. Future works
Gas studyGas studyCFCF44 properties properties
Background studyBackground studyγ-ray discriminationγ-ray discrimination
Study of the diffusion effectStudy of the diffusion effect influence on the sensitivityinfluence on the sensitivity
Energy CalibrationEnergy Calibrationtrack length v.s. energytrack length v.s. energy
5. Conclusions5. Conclusions
WIMP-wind measurementWIMP-wind measurement idea : NOT NEWidea : NOT NEW
μ-PIC has a fine pitch (400 μm)μ-PIC has a fine pitch (400 μm)
Micro-TPCMicro-TPC sensitive to SD and SIsensitive to SD and SI
factor 10 forward/backward asymmetryfactor 10 forward/backward asymmetry
CFCF44 5σ detection possibility 5σ detection possibility
precise studies to doprecise studies to do
diffusion for diffusion for 50×50×50cm50×50×50cm33 Micro-TPC Micro-TPC
~ 10 cm/μsec
50 cm t ~ 5μsec
drift velocity of e- in pure CF4
Dtr 6)( D: diffusion coefficient t: drift time
diffusion coefficient: D ~ 1.5×10-3 cm2/μsec
)(r ~ 2 mm
It’s not so large
PreamplifierPreamplifier - ATLAS amplifier shaper - ATLAS amplifier shaper
discriminator (discriminator (ASDASD) chip ) chip (64ch/card)(64ch/card)
7.7 Mcps7.7 Mcps
X-ray intensity[mA]
DAQ rate[M
Hz] 8
030cm30cm
40cm40cm
Readout electronicsReadout electronics
Position encoding modulePosition encoding module - 5 - 5 FPGAsFPGAs 40MHz clock 40MHz clock
track direction is track direction is importantimportant
track onlytrack only
track+directiontrack+direction
F/B ~ 5F/B ~ 5
F/B ~ 1.3F/B ~ 1.3
Expected rateExpected ratethreshold: 40keVthreshold: 40keV
WIMP mass: 50 GeV for F, ArWIMP mass: 50 GeV for F, Ar 100GeV for Xe100GeV for Xe WIMP-WIMP- p p cross section : 0.1 pb for SDcross section : 0.1 pb for SD 1010-6 -6 pb for SIpb for SI
gasgas pressurepressure[torr][torr]
densitydensity[g/m[g/m33]]
raterate[cpd/kg][cpd/kg]
EventEvent(10m(10m33×1yr)×1yr)
CFCF44 2020 9090 0.210.21 260260
ArAr 2020 4747 0.0340.034 4.14.1
Xe(SD) Xe(SD) 55 1010 0.0110.011 1.41.4
Xe (SI)Xe (SI) 55 3838 0.0790.079 9.69.6
S/N calculation S/N calculation threshold: 40keVthreshold: 40keV
WIMP mass: 50 GeV for F, ArWIMP mass: 50 GeV for F, Ar 100GeV for Xe100GeV for Xe WIMP-WIMP- p p cross section : 0.1 pb for SDcross section : 0.1 pb for SD 1010-6 -6 pb for SIpb for SI
gasgas EventEvent(30m(30m33×3yr)×3yr)
F/B F/B ratioratio
ModulationModulation
(σ)(σ)
n BG n BG ×1/100×1/100
CFCF44 23402340 1414 20σ20σ 40σ40σ
ArAr 3737 1111 0.4σ0.4σ 3σ3σ
Xe(SD) Xe(SD) 1313 55 0.1σ0.1σ 1σ1σ
Xe (SI)Xe (SI) 8686 55 0.4σ0.4σ 5σ5σ
Expected 95 % C.L. sensitivitiesExpected 95 % C.L. sensitivities
Spin-Dependent Spin-Dependent Spin-Independent Spin-Independent
Xe 30 m3, 3 years35cm water shield
Xe 10 m3, 1 yearnoshield
CF4 10 m3, 1 yearnoshield
CF4 30 m3, 3 years35cm water shield
spectrum spectrum
Threshold dependency of F/BThreshold dependency of F/B
gas: CF4
WIMP-p: 0.1 pb
forward/backward increases with theincreases with the threshold energythreshold energy