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Directional Dark Matter Detection with the DMTPC Experiment
Michael Leyton
Feb. 18, 2016
Directional detection
A correlated signal would be unambiguous proof
WIMPS have a preferred direction in galactic coordinates
Sidereal modulation in direction up to 10x annual modulation
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arXiv:1602.03781 (2016)
MIMAC
NEWAGE
DRIFT
DMTPC D3
Emulsions
ZnWO4
HPXe
CYGNUS
Dark Matter Time Projection Chamber m3
Ground/anode (amplification region)
Cathode
Fieldcage
DMTPC concept
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E
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DMTPC concept
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DMTPC concept
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DMTPC concept
PMT
CCD
Amplifiers
DMTPC CCD readout
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each pixel: 240 um x 240 um
Track length of a 50 keVr F recoil in 30 torr CF4: 2.5 mm
• 10-L detector:
- Deployed underground at WIPP
- Spin-dependent (SD) dark matter-nucleon cross section limit
• 4-shooter (20 L):
- Multi-camera readout
- Low-background materials
- Event discrimination with charge readout
• Canary chamber (< 1 L):
- Triple-mesh amplification region
DMTPC prototypesS. Ahlen et al., Phys. Lett. B695:124-129 (2011)
J. Battat et al., Nucl. Instrum. Meth. A755:6-19 (2014)
C. Deaconu, Ph.D. thesis, MIT (2015)
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J. Lopez et al., Nucl. Instrum. Meth. A696:121-28 (2012)
Directional sensitivity
For scaling up and improving directional sensitivity, need to
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4sh data
Theory
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Charge readout for E measurement, background subtraction and trigger
1-sh side: 2 x TPC 1 x CCD 4 x PMT
4-sh side: 2 x TPC 4 x CCD 1 x PMT
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Amplification region
Cathode
Field cage
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Fabrication and Integration
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35 cm
Am-241 α track
Summed bias image
CCD interaction
0.7 mm
Some data!
Anode CSP pulse
Illuminated image
Gain calibration
Measured gas gain (multiplication) using Fe-55 source and amplitude of anode charge signal
mV2 4 6 8 10 12 14 16 18 20
Entries
0
100
200
300
400
500
PRELIMINARY 3DMTPC m
Fe calibration55Run 382, Mean 0.010 mV±7.414 σ 0.007 mV±0.321
dof/n2χ 1.81
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Anode voltage [V]680 690 700 710 720 730 740
Mea
n pe
ak a
mpl
itude
[mV]
0
10
20
30
40
50Fe calibration55Runs 640-719,
Slope: -1 0.001 V±0.029 PRELIMINARY 3DMTPC m
)3G
as G
ain
(x10
0
50
100
150
200
250
10-L4-sh
m3
Projected directional sensitivity
Simulated axial spread for WIMPs
Simulated head-tail efficiency for WIMPs+
=
Probability of rejecting isotropy with n signal events18
Assuming 30 torr CF4 target and 100K gas gain
22˚at 80 keVr
60% at 80 keVr
Projected directional sensitivity
=
Probability of rejecting isotropy with n signal events
—> Current level of sensitivity from counting experiments [σp = 1 fb] can be achieved with 300 (500) m3-years, for a WIMP mass of 1000 (100) GeV.
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Projected directional sensitivity
… or 3 (5) 100-m3-years!
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Summary• Full detector model, validated with data, now available for DMTPC
• Developed directional sensitivity metric incorporating head-tail and axial measurements
• 300 (500) m3-years necessary for 3σ detection of 1 fb 1000 (100) GeV WIMPs
• 1 (out of 4) TPC’s installed into m3 chamber
• Demonstrated proof-of-principle at m3 scale using modular, scalable design
• Next steps:
• Complete fabrication and continue commissioning studies
• Study directional performance on the surface
• Deploy at SNOLAB in 2016-17
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Some food for thought …
How does the effort needed to build a large directional experiment balance against the confidence gained from an annual signal collected over several years?
Backup Slides
4 x FLI ProLine 9000 1 x Spectral 1100S
2 x CAEN 6730 WFD5 x Hamamatsu R1408
Front-illuminated Kodak sensor 3056 x 3056 pixels 12 um pixel size 0.2 ¢/channel
Back-illuminated Fairchild sensor 4096 x 4096 pixels 15 um pixel size 0.5 ¢/channel
Read noise: 9 e- RMS @ 1 MHz < 0.01 e-/pixel/sec @ -40 C
Read noise: 7 e- RMS @ 1 MHz < 1 e-/pixel/sec
14 bit 250 MHz bandwidth Little to no dead time
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Amplification region
Cathode
Field cage
z
rV/cm
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TRIM track
x
0 1 2 3 4 5 6 7
01
23
45
67
-2
-1
0
1
2
3
4
200 keV 19F30 torr CF4
Nuclear/ionization losses only (MC)
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TRIM track
x
0 1 2 3 4 5 6 7
01
23
45
67
-2
-1
0
1
2
3
4
200 keV 19F30 torr CF4
DD source data vs. MC
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