1. J. Helsby, P. Ford, R. Hoch, K. Gnanvo, R. Pena, M. Hohlmann, D. Mitra
Muon Tomography for Detection of Nuclear Contraband with High Performance Computing Infrastructure FAS - Mar. ‘08
J. Helsby, P. Ford, R. Hoch, K. Gnanvo, R. Pena, M. Hohlmann, D. Mitra
Florida Tech
Florida Academy of Sciences, Jacksonville University, Jacksonville, FL, Mar 14, 2008

2. J. Helsby - Florida Academy of Sciences, Jacksonville University, FL
Introduction
Muon Tomography first used by Luis Alvarez to look for hidden chambers in the pyramids at Giza in the 1960s.
Use GEANT4/CrY to simulate scenarios of shipping containers carrying nuclear contraband.
Use an algorithm to reconstruct the scattering angles and scatter positions associated with those angles.
Feasibility Study of possible detections (resolution required, ability to differentiate materials etc.).
3/14/2008
J. Helsby - Florida Academy of Sciences, Jacksonville University, FL

3. J. Helsby - Florida Academy of Sciences, Jacksonville University, FL
Cosmic Ray Muons
Mass=105.7 MeV
 Flux at Sea Level = 10,000 muon/m2/min
Zenith angle distribution about 0º
Average Energy at Sea Level = 4 GeV
Why muons?
Low radiation dose
Noninvasive
No source
Penetrate through shielding
3/14/2008
J. Helsby - Florida Academy of Sciences, Jacksonville University, FL

4. J. Helsby - Florida Academy of Sciences, Jacksonville University, FL
Muon Scattering
Measure the deflection of a muon trajectory using detectors on the top and bottom of the chamber.
Charged particles scatter more with higher Z thus the scattering angles from the muon scattering give indications of what materials are present inside the container.
[Los Alamos Research Quarterly Spring ‘03]
3/14/2008
J. Helsby - Florida Academy of Sciences, Jacksonville University, FL

5. Monte Carlo Simulations
We use GEANT4, a toolkit developed by CERN and written in C++, to model the passage of muons through various scenarios.
We use CRY (Cosmic RaY) which is a muon generator developed by LLNL to describes the energy and angular dependence of muons in the atmosphere.
Set of three GEM (Gas Electron Multiplier) Detectors
Targets
3/14/2008
J. Helsby - Florida Academy of Sciences, Jacksonville University, FL

6. J. Helsby - Florida Academy of Sciences, Jacksonville University, FL
POCA
Point of Closest Approach (POCA) is the algorithm used to reconstruct the scatter points in the material.
3/14/2008
J. Helsby - Florida Academy of Sciences, Jacksonville University, FL

7. J. Helsby - Florida Academy of Sciences, Jacksonville University, FL
Scenario: Low Z & High Z
With GEM Detector
Z [mm]
Z [mm]
“Perfect” Detector
X [mm]
Al Box: 20 cm x 20 cm x 20  cm
U Box: 10 cm x 10 cm x 10 cm
2.5 Million Events = 10 Min Exposure Time
X [mm]
3/14/2008
J. Helsby - Florida Academy of Sciences, Jacksonville University, FL

8. Importance of Resolution
Results appear to show resolution to distinguish Uranium blocks well from low-Z materials such as Al needs to be around 50 microns.
Normalized Angle Range
Normalized Angle Range
Z [mm]
Z [mm]
X [mm]
X [mm]
Z [mm]
Z [mm]
X [mm]
X [mm]
X [mm]
3/14/2008
J. Helsby - Florida Academy of Sciences, Jacksonville University, FL

9. J. Helsby - Florida Academy of Sciences, Jacksonville University, FL
Scenario: High Z
Normalized Angle Range
Normalized Angle Range
Z [mm]
Z [mm]
Z [mm]
X [mm]
X [mm]
As expected, when looking at similar Z materials next to one another, it is not apparent which is the Uranium.
The dimensions of the boxes are visible in the 50 micron resolution only.
3/14/2008
J. Helsby - Florida Academy of Sciences, Jacksonville University, FL

10. J. Helsby - Florida Academy of Sciences, Jacksonville University, FL
Conclusion
Muon radiography is a highly promising method for detecting heavy materials in a low or medium Z background.
Detector resolution should be at or better than 50 microns in order to resolve 1 Liter objects well.
Future work:
Advanced analysis needs to be done to determine how well similar Z materials can be distinguished from one another.
Develop new reconstruction algorithm
Future challenge:
Developing large enough GEM detectors to achieve the 50 micron resolution.
3/14/2008
J. Helsby - Florida Academy of Sciences, Jacksonville University, FL

11. Extra
Florida Academy of Sciences, Jacksonville University, Jacksonville, FL, Mar 14, 2008

12. Mult. Coulomb Scattering
3/14/2008
J. Helsby - Florida Academy of Sciences, Jacksonville University, FL

13. J. Helsby - Florida Academy of Sciences, Jacksonville University, FL
Smearing
The spatial resolution of the GEMs detectors is simulated in GEANT4 by smearing the position coordinates at the GEMs in the x and y directions with a Gaussian shape random number generator. For example:
X = x + Res
Res = Gaussian random number with a standard deviation = 50, 100, 200 microns
The 4 sets of coordinates data are generated in the same simulation run
3/14/2008
J. Helsby - Florida Academy of Sciences, Jacksonville University, FL

14. J. Helsby - Florida Academy of Sciences, Jacksonville University, FL
Muon Tomography
3/14/2008
J. Helsby - Florida Academy of Sciences, Jacksonville University, FL