1. Prototype of a Muon Tomography Station with GEM Detectors for Detection of Shielded Nuclear Contraband
Michael Staib1
V. Bhopatkar1, W. Bittner1, K. Gnanvo1,2, L. Grasso1, M. Hohlmann1, J. B. Locke1, J. Twigger1
1Dept. of Physics & Space Sciences, Florida Institute of Technology
2 now at University of Virginia
2012 April APS Meeting, Atlanta, GA

2. Outline Concept of Muon Tomography and previous work.
Cubic-foot MTS with GEMs
Experimental Results
Future Work
Concept of Muon Tomography and previous work.
Prototype cubic-foot Muon Tomography Station (MTS) with GEM Detectors.
The Gas Electron Multiplier (GEM) detector.
DAQ electronics and analysis software.
Experimental tomographic reconstructions of shielded and unshielded high-Z materials using this prototype.

3. Reconstruction Algorithm
Muon Tomography Concept
Outline
Muon Tomography
Cubic-foot MTS with GEMs
Experimental Results
Future Work Fe U
Large
Scattering
Small μ
Iron
Uranium
Incoming muons (from natural cosmic rays)
Note: Angles Exaggerated! μ μ
Reconstruction Algorithm
Point of Closest Approach
(POCA)
Object
Tracking detectors
Multiple Coulomb scattering to 1st order produces Gaussian distribution of scattering angles θ with width σ = Θ0:

4. Original idea from Los Alamos (2003): Muon Tomography with Drift Tubes
Outline
Muon Tomography
Cubic-foot MTS with GEMs
Experimental Results
Future Work Pb W
INFN
Brass Cu Fe Al
Reconstruction of 1 inch thick Pb letters
CMS
1.4 m
4.3 m 1 2 3
Original idea from Los Alamos (2003): Muon Tomography with Drift Tubes
INFN : Muon Tomography with spare CMS Muon Barrel Chambers (Drift Tubes)
Decision Sciences Int’l Corp.:  Multi-Mode Passive Detection System, MMPDSTM
from Decision Sciences public web pages
J.A. Green, et al., “Optimizing the Tracking Efficiency for Cosmic Ray Muon Tomography”, LA-UR , IEEE NSS 2006.
S. Presente, et al., Nucl. Inst. and Meth. A 604 (2009)

5. Muon Tomography Station Using GEMs
Compact Cubic-Foot
Muon Tomography Station Using GEMs
Outline
Muon Tomography
Cubic-foot MTS with GEMs
Experimental Results
Future Work
Plastic Scintillator (Trigger)
Triple-GEM Detector
1 ft3
active
volume
30 cm

6. GEM foil under electron microscope
Gas Electron Multiplier (GEM) Detector
Outline
Muon Tomography
Cubic-foot MTS with GEMs
Experimental Results
Future Work
GEM foil under electron microscope V
~400 V μ- e-
M.C Altunbas, et al., Nucl. Inst. and Meth. A 515 (2003)
F. Sauli, Nucl. Inst. and Meth. A 386 (1997)
Gas Gain ~ O(104)

7. Assembled GEM Detector
Triple-GEM Detector for MT station
Outline
Muon Tomography
Cubic-foot MTS with GEMs
Experimental Results
Future Work
30 cm x 30 cm triple-GEM detectors
Follows design for COMPASS at CERN
Ar/CO2 70:30 mixture
X-Y Cartesian 400 μm pitch
~50 µm spatial resolution for perpendicular tracks
Compact detector, low material budget
Drift Cathode
GEM foil
FR4 Spacer Frame
400 μm
X-Y Readout
80 μm
400 μm
340 μm
Readout Strips
(bottom layer)
Assembled GEM Detector
Insulating Layer
Readout Strips
(top layer)
Support
COMPASS Design
Nucl. Inst. and Meth. A 490 (2002) 177–203

8. DAQ Electronics
Outline
Muon Tomography
Cubic-foot MTS with GEMs
Experimental Results
Future Work
Scalable Readout System (SRS) developed by the RD51 collaboration at CERN.
Currently 11 teams using SRS for different applications using MPGDs.
Florida Tech is currently the largest user with ~12k channels of analog readout.
HDMI
Gb Ethernet
APV25 Hybrid
ADC
FEC
128 channel APV25 chip
192-deep analog sampling memory
Master/slave configuration
Diode protection against discharge
RD51 standard 130-pin Panasonic connector interfaces to detector
HDMI mini (type C) connector
DAQ Computer
2 x 12-Bit Octal ADC
8 x HDMI input channels (16 APV hybrids)
Virtex LX50T FPGA
SFP/Gb Ethernet/DTC interface
NIM/LVDS GPIO (trigger, clock synch, etc.)
Data Acquisition using DATE CERN)
Support added for data transfer via UDP
Slow control via ethernet
Online and offline analysis using custom package for AMORE CERN)

9. Detector Characterization using AMORE
2D Hit Map
Charge Sharing
Signal to Noise Ratio
Note: Crossed structure due to spacer frames
Cluster Multiplicity
Cluster Size
Cluster Charge Distribution
Mean = 1.2 Clusters
Mean = 4.7 Strips

10. Material Discrimination: Scenario
Outline
Muon Tomography
Cubic-foot MTS with GEMs
Experimental Results
Future Work
Lead
Z = 82
Density = 11.3 g/cm3
Tungsten
Z = 74
Density = 19.3 g/cm3
Depleted Uranium
Z = 92
Density = 19.1 g/cm3
6mm Al shielding
Iron
Z = 26
Density = 7.9 g/cm3
Tin
Z = 50
Density = 5.8 g/cm3

11. Simple Scattering Density (Degrees / cm3)
Material Discrimination: Result
Outline
Muon Tomography
Cubic-foot MTS with GEMs
Experimental Results
Future Work
-55 mm < z < -15 mm
Min. # of muon per voxel = 2
Lead
Tungsten
Tin
Iron
Uranium
Voxel Size: 2 x 2 x 40 mm3
Simple Scattering Density (Degrees / cm3)
Uranium
Tungsten
Lead
Tin
Iron
157.8
115.3
101.0
68.9
61.3
155,104 Reconstructed Tracks

12. Material Discrimination: Result
XZ Slices U Sn Fe Pb W +Y +X Pb W
-70 mm < Y < -30 mm
-20 mm < Y < 20 mm
30 mm < Y < 70 mm
YZ Slices Sn Fe Sn Pb U Fe W
-70 mm < X < -30 mm
-20 mm < X < 20 mm
30 mm < X < 70 mm
155,104 Reconstructed Tracks

13. Uranium with Brass Shielding
Outline
Muon Tomography
Cubic-foot MTS with GEMs
Experimental Results
Future Work
The shielded uranium block can clearly be seen in the reconstruction
187,731 Reconstructed Tracks
40 mm XY slices with Z decreasing by 5mm each frame

14. Future Work
Outline
Muon Tomography
Cubic-foot MTS with GEMs
Experimental Results
Future Work
Increase the number of GEM detectors per tracking module to improve reconstruction.
Redesign support structure to allow more freedom in detector orientation.
Implement statistical reconstruction methods and POCA clustering algorithms.
Improve tracking and sensor alignment methods in the AMORE analysis package.
Include a measurement of muon momentum in the reconstruction.
Scale up! (Next goal is ~1 m3 active volume)

15. Thanks!
Questions?
Disclaimer: This material is based upon work supported in part by the U.S. Department of Homeland Security under Grant Award Number 2007-DN-077-ER The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Department of Homeland Security.

16. Backup Slides

17. Image Resolution Study: Imaging a gap separating W and Pb blocks
0 mm
2 mm
4 mm
115,834 muons
94,719 muons
111,036 muons
6 mm
8 mm
107,506 muons
121,634 muons

18. Scattering Density (deg/cm3)
0 mm
2 mm
4 mm
6 mm
8 mm
Statistically significant signal with 8mm spacing
Analysis Region