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