An MPGD Application Muon Tomography for Detection of

An MPGD Application: Muon Tomography for Detection of Nuclear Contraband Marcus Hohlmann, P. Ford, K. Gnanvo, J. Helsby, R. Hoch, D. Mitra Florida Institute of Technology 2 nd meeting of RD 51 collaboration, Institute Henri Poincaré, Oct 13, 2008 M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris

Outline • Nuclear Contraband • Muon Tomography – Basic Concept – Existing Work – MPGDs for MT • Simulation of an MT station – Computing, Generation, Simulation, Reconstruction – Results on Expected Performance • Plans for R&D on MT Prototypes with MPGDs M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris

The Nightmare Scenarios • Terrorist smuggle highly enriched uranium (HEU) or plutonium across borders and destroy a city by detonating a nuclear bomb, or • Terrorists smuggle highly radioactive material into a city and disperse it with a conventional explosion (“dirty bomb”) making portions of the city uninhabitable. T. B. Cochran and M. G. Mc. Kinzie, Scientific American, April 2008 M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris

Challenge in Detecting Nuclear Contraband ~ 800 Radiation Portal Monitors (n, γ) in U. S. Sci. Am. , 4/2008 HEU can be hidden from conventional radiation monitoring because emanating radiation is relatively easy to shield within regular cargo • In 2002, reporters managed to smuggle a cylinder of depleted uranium shielded in lead in a suitcase from Vienna to Istanbul via train and in a cargo container through radiation monitors into NY harbor. Cargo was flagged for extra screening, but DU was not sensed. • In 2003, used route Jakarta – LA, same result Sci. Am. , 4/2008 6. 8 kg DU • IAEA: During 1993 -2006, 275 confirmed incidents with nuclear material and criminal intent; 14 with HEU, 4 with Pu. Scientific American, April 2008 M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris

A Potential Solution: Muon Tomography Incoming muons (μ±) Note: angles are exaggerated ! (from natural cosmic rays) Q=+92 e μ μ ntainer o Cargo c Q=+26 e Θ 235 92 U Θ 56 26 Fe Regular material: small scattering angles hidden & shielded Θ high-Z nuclear material μ Θ tor Detec Tracking Main ideas: HEU: Big scattering angles! Approx. Gaussian distribution of scattering angles θ with width θ 0: μ tracks • Multiple Coulomb scattering is ~ prop. to Z and could discriminate materials by Z • Cosmic ray muons are ubiquitous; no artificial radiation source or beam needed • Muons are highly penetrating; potential for sensing high-Z material shielded by Fe or Pb • Cosmic Ray Muons come in from many directions allowing for tomographic 3 D imaging M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris

MT Work by Other Groups 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) CMS Muon barrel J. A. Green et al. , “Optimizing the Tracking Efficiency for Cosmic Ray Muon. Tomography”, LA-UR-06 -8497, IEEE NSS 2006 S. Pesente et al. , SORMA West 2008, Berkely, June 2008 Pb W Brass Cu Efforts also by Tsinghua U. , IHEP Protvino, Decision Science (U. S. commercial) M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris Fe Al

Fl. Tech Concept – MT with MPGDs Use Micro Pattern Gaseous Detectors for tracking cosmic ray muons ADVANTAGES: q excellent spatial resolution improves scattering angle measurement on Cargo c PG D Tr ac ki ng q compact detector structure allows for more compact MT station design • thin detector layers • small gaps between layers • smaller scattering in detector itself De te ct o r hidden & shielded CHALLENGES: q requires large-area MPGDs (MPGDs as muon detector !) M tainer Θ high-Z nuclear material μ Θ MPGD, e. g. GEM Detector e cking D q large number of electronics channels (but occupancies very low) Tra MPGD μ tracks ~ 1 cm e- q low rates from cosmics, need good eff. q cost (but access to funding outside HEP) That’s why we’re here today! M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris Readout electronics F. Sauli

Where’s Florida Tech ? Cape Canaveral & NASA Kennedy Space Center Orlando (IEEE NSS ‘ 09) Florida Tech Photo credit: NASA STS-95 Physics & Space Sciences Dept. Small, private university on the “Space Coast” • founded by a physicist in 1958 • ~2, 500 undergrads & ~2, 500 graduate students Muon Tomography Group: • 2 faculty (HEP, Comp. Sci. ) • 1 post-doc • 2 graduate students • 4 undergraduates • (1 electronics engineer) M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris

R&D Program Three-year program: 1. Build a Linux cluster for simulation work (160 slots; on Grid via OSG; could be made available to RD 51!) 2. Detailed MC simulation of MT station 3. Prototyping with increasing detector size 4. Performance measurements We are currently here Funded by Domestic Nuclear Detection Office (DNDO) in the U. S. Department of Homeland Security (DHS) (Disclaimer: The views and conclusions contained in this presentation 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. ) M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris

Monte Carlo Simulation Typical Geometry: • Generate cosmic ray muons with CRY Side View 10 m (Lawrence Livermore NL) • Simulate geometry, target, detector, tracks with GEANT 4 Muons originate here over an area of 1, 000 cm 2 (1 M muons in ~1 min exposure) 4 m GEM detector planes Basic Target • Take advantage of detailed description of multiple scattering effects within GEANT 4 (follows Lewis theory of multiple scattering) 3 GEM layers with 5 mm gaps between layers Top View + - 10 m 5 m 4 m 3 m GEMs M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris CRY plane

Geometrical Acceptance MT station type Top View (x-y plane) Side View (x-z plane) Top & bottom detectors only z 3 m y x Top, bottom & side detectors z y x Traversal of station by cargo M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris

Scattering Reconstruction • Simple reconstruction algorithm using Point of Closest Approach (“POCA”) of incoming and exiting 3 -D tracks • Treat as single scatter • Scattering angle: M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris

Scattering Angle Distributions Results from high-statistics MC samples M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris

Basic Statistic for Z-discrimination: Mean Scattering Angles MT Station & Scenario: • Top, bottom & side det. • 40 cm 10 cm targets; 5 materials • Divide volume into voxels Results: • Good Z discrimination (even for Pb vs. U) • Targets imaged • Resolution matters! W U Pb Pb Al Fe W U Pb Al Pb Fe Al M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris Fe

Effect of Detector Material Comparison: 1. All MT station materials set to vacuum 2. Station volume filled with air; GEMs modeled by 5 mm Kapton material Result: Minor increase in mean scattering angles and image smearing M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris

Significance of Excess – 10 min • 10 min exposure • Compare targets against Fe background (steel) using Fe samples w/ high statistics • Significance for all voxels with an excess at ≥ 99% confidence level over Fe standard: Sig W U U W Pb Pb > 5σ in ALL high-Z voxels Sig U W Pb M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris

Significance of Excess – 1 min • 1 min exposure • Significance for all voxels with an excess at ≥ 99% confidence level over Fe standard • Still doing ok with 50 micron resolution • With 200 micron resolution we are losing sensitivity Sig U W Pb Pb Most U voxels > 3σ Sig U W Pb Trouble… M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris

Identifying Uranium at 99% C. L. • Test hypothesis that voxels with an excess over Fe actually contain U • Flag only voxels where mean voxel is within 99% confidence interval around expected mean U for Uranium (based on high-statistics U samples) 1 min exposure 10 min exposure W U Pb W U false Pb pos. correct pos. ID Pb target rejected by U hypothesis ! W Pb false positives U W U some Pb false pos. correct pos. ID false pos. M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris false negative !

Shielded Targets among Stack of Shielding Plates Reconstructed scattering angles (normalized) Side Views Al plates U Pb 10 min exposure Perfect resolution Decent Signal 15 cm Targets: 10 cm U cube encased by 2. 5 cm Pb on each side 10 cm Pb U Fe plates 15 cm thick shielding plates made of Al or Fe “Vertical Clutter” Scenario M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris No Signal

Advanced Reconstruction Algorithm Maximum Likelihood Method • Reproducing Los Alamos Expectation Max. algorithm (L. Schultz et al. ) • Input: Use lateral shift Δxi in multiple scattering as additional information on top of scattering angle θi for each (i-th) muon track • Output: Scattering density λkfor each (k-th) voxel of the probed volume – λ relates the variance of scattering with radiation length (or Z value) of the respective material • Procedure: Maximize log-likelihood for assignment of scattering densities to all independent voxels given observed tracks – Analytical derivation leads to an iterative formula for incrementally updating λk values in each iteration of First reconstruct 20 cm 40 cm U target θi Δxi Work in Progress… M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris

Conclusion & Plans • Muon Tomography with MPGDs is a promising technology for detecting shielded nuclear contraband as indicated by our MC studies – Good Z-discrimination expected for • U vs. Fe with 1 min exposure • U vs. Pb with 10 min exposure – Resolution and statistics dominate expected performance • MPGDs – offer significant performance improvement over drift tube stations to superior resolution – allow much more compact MT stations • Plans: – – Finalize simulation results; continue developing algorithms (CS people) Move from simulation to experimentation Build increasingly large MPGD prototypes and test them for MT Partner with RD 51 collaborators in this development of MPGDs for large-area muon chambers including electronics development We expect this experimental program to be a major challenge ! M. Hohlmann - Muon Tomography, RD 51 Collaboration meeting, IHP, Paris due