1. J. Twigger, V. Bhopatkar, E. Hansen, M. Hohlmann, J.B. Locke, M. Staib
Tomographic Imaging of nuclear contraband using a cubic foot muon-tomography station
J. Twigger, V. Bhopatkar, E. Hansen, M. Hohlmann, J.B. Locke, M. Staib
Florida Institute of Technology
High Energy Physic Lab A

2. Overview Reconstruction Design
Physics of a Gaseous Electron Multiplying Detector
Purpose
Visual Representation of Muon Scattering
Presenting Multiple Images on the Discrimination of Materials with Different Atomic Numbers (Z) and Density
Current plans for Improvement
The near future

3. Reconstruction
The ultimate goal of reconstruction is to find the Point of Closest Approach (POCA) and corresponding scattering angle.
Using an incoming and outgoing track we are able to calculate the amount of scattering a muon experiences while travelling through dense materials.
This scattering is small, requiring extremely accurate spatial resolution from the detectors.

4. Point of Closest Approach
POCA Reconstruction
Scattering Angle
Point of Closest Approach . θ1

5. The Muon Tomography Station
Incoming muon track
Active Volume
Scattering
Outgoing muon track

6. +y  +x  A View from the Outside
Each readout panel contains 768 readout strips in X and Y plane
30 cm x 30 cm triple-GEM detectors
+y 
+x 

7. Exploded View of the GEM Detector
Drift Region
Each GEM is filled with
an Argon/Carbon Dioxide mixture during operation
GEM foil 1
Spacer Frame

8. The Inner Workings

9. Differentiating Materials
Lead: 82 Z
Density: g/cm3
Tungsten: 74 Z
Density: g/cm3
Uranium: 92 Z
Density: 19.1 g/cm3
Tin: 50 Z
Density: 7.31 g/cm3
Iron: 26 Z
Density: 7.87 g/cm3

10. Five Target Reconstructed Images

11. Discrimination and Shielding
The Brass Shield
Top-View
Uranium Target at the Middle

12. Identifiable Shielding
Outer Shielding
Small Gap

13. The Lead Shielded Target
Inside sit four different blocks, including a large cube of depleted uranium.

14. Looking down on a Lead Brick

15. In Summary
The amount of scattering is proportional to the atomic number and density of the material. Allowing for the imaging of material that is surrounded by commonly used metals like Iron or Steel.
The ability to image such dense materials as uranium will provide a more effective way of detecting illegal nuclear material.

16. The Near Future Experimenting with new Detector Geometries and Designs
Live Display of targets in the MTS Station
Experimenting with new readout structures on the miniature GEM detectors