75th Annual MeetingMarch 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 32901 0

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 235U.

How can we detect shielded nuclear contraband?

Sci. Am., 04/2008

Nuclear contraband issmuggled across borders.

Current radiation scannersuse gamma and neutronemissions to detect nuclearcontraband.

About 800 radiation portalmonitors in the U.S.

2

Muon Tomography Concept

56FeΘ

Θ

Incoming muons (μ±)

μ

Θ

Θ

Note: angles are exaggerated !

(from natural cosmic rays)

Cargo container

hidden &shieldedhigh-Znuclearmaterial

μ tracks

Regular material (low/medium Z):Small scattering angles

High-Z material: Big scattering angles!

μQ=+92e

Q=+26e

235U92

26

Tracking Detector

Idea: Use multiple scattering of charged particles in matter to detect high-Z material

Tracking Detector

3

Origin of Muon TomographyOriginal 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)Ac

tive

Volu

me

θ

Point of Closest Approach

(POCA)in 3D Space

a

b

Incoming Vector

Outgoing V

ector

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

θ1

θ2

Voxel color indicatesmean scattering angle in voxel

< θ > 6

Activ

e Vo

lum

e

Muon Tomography Station

Minimal PrototypeMuon Tomography Station (MTS)

withGas 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 cm2 to be read out.

30 x 30 cm2

8

Active Volume

Reconstructing the Active Volume

Voxels

9

Min. MTS Reconstruction with Real Data3 x 3 x 3 cm3 Iron Cube 3 x 2.8 x 3 cm3 Lead Block

10

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

11

0

1

2

3

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

ft3 MTS

15

ft3 MTSBeing assembled

at CERN right now!

Lateral DetectorsImprove Muon Coverage

Improve z Resolution

16

FePbTa

ft3 MTS Simulation Reconstruction

Same targets imaged withminimal prototype MTS.

17

Fe

Pb

Ta

ft3 MTS Simulation Reconstruction (Top view)

18

ft3 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

ft3 MTS

A2

ft3 MTS in the Lab

A3

Coverage Concept

Active Volume

3D Voxel

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

1

0

0

0

0

1

1

1

0

1

1

1

2

2

0

0

0

0

0

Higher coverage → Higher statistics for reconstruction

Muon Tracks

A5