Transcript Development of GEM Detectors for Muon Tomography

Development of GEM
Detectors for Muon
Tomography
N. Leioatts, T. Garlick, A. Moss, A. Quintero, M.
Hohlmann
Department of Physics and Space Sciences
Florida Institute of Technology
Gas Electron Multiplier (GEM)
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Particle detector technique
(1).
Constructed of Kapton foil
clad in copper on both
sides, with holes through
layers (1).
Voltage applied
High electric field in holes
Avalanche of ions and ee- collected (2).
(1) Sauli, F.; NIM A386 531, 1997.
(2) http://cerncourier.com/cws/article/cern/27921
Our GEM
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Triple GEM
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Limit to Gain per foil
(sparking)
4 foils made
Planned Use: Homeland
Security (Muon Tomography for
detection of nuclear contraband. J.
Helsby, et al. FAS 2008)
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70:30 Ar:CO2
55Fe Source for testing
 Emits monoenergetic 5.9 KeV X-ray
Our Detector
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HV circuit
Readout Amplifier
Oscilloscope
Construction
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Arrive
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Stretched
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On Machined G10 Frames
Mounted
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With Stycast
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Cut
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Assembled
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On lid of detector
Then It Works!!
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Not so much
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Large leakage current
Peak occurs much
lower than GEM
operating voltage (3)
(3) F. Murtas. LNF-INFN. Frascati (2002)
Areas that Needed Improvement
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GEMs Sparking
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Box Pressure
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Gluing
Larger Clamps
Gas System Testing
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Amplifier Readout
Gauge Pressure (kPa)
3.00
2.50
2.00
Pressure Test 1
Pressure Test 2
Pressure Test 3
1.50
Pressure Test 4
1.00
0.50
0.00
0
100
200
300
Time (s)
400
500
Improvements
Pressure Decrease with Time
Gas Leakage
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Sturdier Steel Frames
8” C-clamps
Stycast
Soldered connector
pins
50
40
Pressure (KPa)
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30
Pressure Before
Gluing
20
Pressure After Gluing
10
0
-4
-2
0
2
Time Elapsed (hrs) (log)
Amplifiers
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Characterized
differential to single
side amplification
Amplifier B, Tested with a Square input
Electric Field Testing
Electric Field vs. Input Voltage
Linear Output from
HV circuit
3000
E-field (V/cm)
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3500
GEM 3+/3GEM 3-/2+
GEM 2+/2GEM 2-/1+
GEM 1+/1-
2500
2000
1500
1000
500
Operating Voltage:
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0
0.000
2.000
4.000
6.000
8.000 10.000 12.000
Vin (V)
Vin ~ 9V
Produces 300V
across a single foil
Output of HV circuit
4500.000
4000.000
Output Voltage of HV Circuit
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3500.000
Gem 3+
3000.000
Gem 3Gem 2+
2500.000
Gem 22000.000
Gem 1+
Gem 1-
1500.000
DC
1000.000
500.000
0.000
0.000
2.000
4.000
6.000
8.000
Input Voltage to Power Supply
10.000
12.000
14.000
Individual Testing
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Motivation: High leakage
current between foils
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Systematic testing of
each foil (4)
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Current drops with time
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As in a capacitor
Foil I shows a larger
leakage current than
Foils III and IV
(4) Barbeau, P.S. et al. NIM A 515 (2003)
Conclusions
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Solved physical (gas) leakage problems
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Still has electrical (current) leakage
problems
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Currently working on this
Future
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Continue individual testing until all foils are
satisfactorily characterized
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Reinstall Detector and continue to
troubleshoot problems until detector works
satisfactorily
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Move to the construction of a larger
detector