75 th Annual Meeting March 2011 Imaging with, spatial resolution of, and plans for upgrading a minimal prototype muon tomography station J. LOCKE, W. BITTNER, L. GRASSO, K. GNANVO, and M. HOHLMANN Florida Institute of Technology, Department of Physics and Space Sciences, 150 West University Blvd, Melbourne, FL

Outline Motivation Background – Concept – Origin – Reconstruction algorithm – Voxelization Prototype – Design – Imaging real targets – Spatial resolution of detectors Upgrade – Design – Monte Carlo simulation 1

Motivation Only 3.25 mm thick lead shielding needed to absorb 99% of gammas emitted by 235 U. How can we detect shielded nuclear contraband? Sci. Am., 04/2008 Nuclear contraband is smuggled across borders. Current radiation scanners use gamma and neutron emissions to detect nuclear contraband. About 800 radiation portal monitors in the U.S. 2

Muon Tomography Concept 56 Fe Θ Θ Incoming muons (μ ± ) μ Θ Θ Note: angles are exaggerated ! (from natural cosmic rays) Cargo container hidden & shielded high-Z nuclear material μ tracks Regular material (low/medium Z): Small scattering angles High-Z material: Big scattering angles! μ Q=+92e Q=+26e 235 U Tracking Detector Idea: Use multiple scattering of charged particles in matter to detect high-Z material Tracking Detector 3

Origin of Muon Tomography Original idea from Los Alamos (2003): Muon Tomography with Drift Tubes INFN Padova, Pavia & Genova: Muon Tomography with spare CMS Muon Barrel Chambers (Drift Tubes) 4

Reconstruction Algorithm (POCA) Active Volume θ Point of Closest Approach (POCA) in 3D Space a b Incoming Vector Outgoing Vector Reconstructed Muon Track Matter in the active volume deflects the muon Scattering Angle 5

Voxelization Detectors Voxels “3D Pixels” (Cubes) Detectors One Voxel Muon Tracks θ1θ1 θ2θ2 Voxel color indicates mean scattering angle in voxel 6 Active Volume Muon Tomography Station

Minimal Prototype Muon Tomography Station (MTS) with Gas Electron Multiplier (GEM) Detectors 7

Detector 0 Active Volume Detector 1 Detector 2 Detector 3 Minimal MTS Limited readout electronics allowed only 5 x 5 cm 2 to be read out. 30 x 30 cm 2 8

Active Volume Reconstructing the Active Volume Voxels 9

Min. MTS Reconstruction with Real Data 3 x 3 x 3 cm 3 Iron Cube3 x 2.8 x 3 cm 3 Lead Block 10

Comparing Real Data to Monte Carlo Simulation Tantalum Cylinder (Real Data)Ta Cylinder (Monte Carlo Simulation)r = 1.5 cm, h = 1.6 cm 11

Target Support Plate Active Volume Residual Reconstructed Muon Path Detector Hits Fit Residuals 12

Determining Spatial Resolution 13

128.3 µm Determining Spatial Resolution 14

ft 3 MTS 15

ft 3 MTS Being assembled at CERN right now! Lateral Detectors Improve Muon Coverage Improve z Resolution 16

Fe Pb Ta ft 3 MTS Simulation Reconstruction Same targets imaged with minimal prototype MTS. 17

Fe Pb Ta ft 3 MTS Simulation Reconstruction (Top view) 18

ft 3 MTS Simulation Reconstruction 19

Summary Muon tomography can be used to detect shielded nuclear contraband. Iron, lead, and tantalum blocks were successfully imaged with a minimal prototype muon tomography station. We estimate our GEM detectors to have 130 µm spatial resolution with preliminary electronics. The next generation muon tomography station will have improved reconstruction abilities. 20

Backup Slides A0

Another View of the Minimal MTS A1

Another View of the ft 3 MTS A2

ft 3 MTS in the Lab A3

Coverage Concept Active Volume 3D Voxel Higher coverage → Higher statistics for reconstruction Muon Tracks A5