search for hidden high-z materials inside containers with ... · search for hidden high-z materials...
TRANSCRIPT
IPRD13 7 - 10 October 2013 Siena, Italy
Paola La Rocca for the Muon Portal Collaboration
Department of Physics, University of Catania
Search for hidden high-Z materials inside containers with the Muon Portal Project
IPRD13 7 - 10 October 2013 Siena, Italy
Presentation overview
Cosmic-ray muons and muon tomography
Ongoing projects
The Muon Portal Project
Overall Design Strip and module Photosensors Readout and DAQ Simulation studies
Image reconstruction
Present status of the Project
IPRD13 7 - 10 October 2013 Siena, Italy
The problem
Containers: employed since 50 years as a standard way to transport goods by ships or trucks
Estimated yearly traffic: 200 M containers (in Catania ~ 15000 container /year)
Safety regulations are more and more demanding a better and fast way to inspect such containers, not possible by traditional techniques
IPRD13 7 - 10 October 2013 Siena, Italy
The problem
Presently only about 1% inspected
X-ray tomography
Based on X-ray absorption (requires high fluxes) Problems to traverse large thickness (Mean free path ~ 25 g/cm2 ~ 2 cm Pb) Mono or two-dimensional, not 3D (require multiple projections)
Other possibilities
Directional imaging with gamma rays Neutron radiography
IPRD13 7 - 10 October 2013 Siena, Italy
Why Muon Tomography Secondary cosmic muons: highly penetrating radiations (even more than X-rays)
“Natural” radiation, hence no additional dose delivered to users and goods
Muon flux at sea level relatively large: 1 cm-2 min-1
Muonic interactions well understood
Muon scattering strongly dependent on
the Z of the material
Each muon may contribute to determine the overall imaging result (contrary to muon absorption techniques)
IPRD13 7 - 10 October 2013 Siena, Italy
Muon Tomography
L. Schultz IEEE NSS Conference Record (2006)
l
IPRD13 7 - 10 October 2013 Siena, Italy
Muon tomograph: basically made by several detection planes, above and below the volume to be inspected
Reconstruction of muon tracks allows, by different methods, to produce a 3D tomographic image
Performance of the system are given in terms of
Sensitive area / volume to be inspected Spatial and angular resolution Time to scan a volume Sensitivity & Efficiency to high-Z objects Sensitivity to false positive Discrimination between high-Z vs low & medium-Z
Muon Tomography
IPRD13 7 - 10 October 2013 Siena, Italy
On-going Projects
Several Projects (INFN Padova, Los Alamos, Florida State Univ.,…) worldwide interested to Muon Tomography
A few detector prototypes already built and tested
Various detection techniques employed Drift chambers Drift tubes GEM
Use of the same technique for similar applications (nuclear waste, orphan sources,…)
IPRD13 7 - 10 October 2013 Siena, Italy
The Muon Portal Project in Catania
Basic architecture based on 8 physical detection planes (4 XY logical planes) segmented into 48 detection modules (1 m x 3m)
Modules segmented into 100 strips of extruded scintillator with double WLS fibre readout
High PDE, high fill-factor Silicon photomultipliers as readout sensors
9600 channels with a readout compression technique
Distance between top and bottom planes 5-7 m
Angular resolution around 3 mrad
6 m 3 m
Plane X
Plane Y
IPRD13 7 - 10 October 2013 Siena, Italy
Mechanical structure
Mechanical structure under control with PLC Monitoring and storage of various parameters Sensors for alignment and alarms
Assembly tools
IPRD13 7 - 10 October 2013 Siena, Italy
Test measurements with strips and WLS fibres
To maximize the light yield and reduce the dark current for SiPM, extensive tests carried out under different conditions with
Various designs of scintillator strips (Fermilab, Amcrys, Uniplast)
Different WLS fibres (Kuraray, St.Gobain) Silicon photomultiplier prototypes from
STMicroelectronics
Lab. measurements in a dark box with an external scintillator trigger
Dark current vs threshold Light yield at various distances (0-3 m) Charge spectra
SiPM
IPRD13 7 - 10 October 2013 Siena, Italy
Various designs of extruded strips tested and simulated by GEANT4
Strip design
Threshold 2 p.e.
Threshold 1 p.e.
IPRD13 7 - 10 October 2013 Siena, Italy
Silicon PhotoMultipliers by STMicroelectronics as photosensors
Compactness Cost-effective Low voltages required High Photon Detection Efficiency to light from WLS fibres High Fill Factor Several prototypes built, customized for this application
Photosensor design
MUON70N Prototype Number of cells: 548 Cell fill factor: 73.8 % PDE ~ 40 % (λ → 500 ÷ 550 nm @ OV = 5 V)
IPRD13 7 - 10 October 2013 Siena, Italy
Basic SiPM characterization
IPRD13 7 - 10 October 2013 Siena, Italy
The SiPM test station @ INAF in Catania
fotodiodo
IPRD13 7 - 10 October 2013 Siena, Italy
Front-end Readout
Combining the information of two WLS fibres Reduction factor for module: 2√N (N number of channels)
(8 planes) x (6 modules) x (100 x 2 WLS) = 9600 channels After channel reduction (8 planes) x (6 modules) x (2√100 ) = 960 channels
IPRD13 7 - 10 October 2013 Siena, Italy
Front-end Readout
Strips WLS SiPM
MAROC
MAROC MAROC (Multi Anode Read Out Chip) No. of channels: 64
For each channel: 8 bit variable gain, preamplifier, shaper
IPRD13 7 - 10 October 2013 Siena, Italy
Data Acquisition
Boards based on FPGA Flex RIO National
Instrument programmable by LabVIEW FPGA module
GPS tagging of the events for possible correlation to other detectors
Acquisition board
IPRD13 7 - 10 October 2013 Siena, Italy
Simulation procedures
Full GEANT4 replica of the detector Cosmic muons modeled with realistic
energy and angular distribution by CORSIKA air shower simulations
Transport of optical photons fully simulated for a subset of events and then parameterized to save CPU time
Reconstruction of hits and cluster in each plane
Single muon tracks and e.m. showers taken into account
After track reconstruction, tomographic images built by several methods
Various scenarios considered
IPRD13 7 - 10 October 2013 Siena, Italy
Simulated scenarios
A “MUON” shape with letters of different materials (U, Fe, Pb, Al) As before, with a heavy scenario with washing machines elements (iron, concrete, ..) surrounding the “MUON” shape About 1 M events simulated for each scenario, with realistic energy and angular distributions of muons
IPRD13 7 - 10 October 2013 Siena, Italy
Event reconstruction and selection
Event reconstruction and selection
Hit selection (threshold on deposited energy) Cluster finding from hit strips Track finding by Kalman Filter algorithm, valid
also for high-multiplicity events
Selection
Single cluster events for tomographic imaging Multicluster events recorded for physics
analysis
IPRD13 7 - 10 October 2013 Siena, Italy
The POCA algorithm
Simplest approach, fast and easy to implement Geometrical point of closest approach between incoming
and outcoming tracks
Ppoca = ½ (Pin + Pout)
Spatial distribution of the scattering centres, weights given by some power of the scattering angle
However: Neglects multiple scattering within the material Poor resolution images Critical behaviour for material located close to
volume borders
Several improvements may be implemented: - Density based clustering algorithms - Two points (2P) correlation analysis
S.Riggi et al., NIM A 728 (2013) 59-68
IPRD13 7 - 10 October 2013 Siena, Italy
The EM-ML method
Better statistical treatment of scattering processes by a log-likelihood method
Volume to be inspected divided into voxels Scattering density defined for each voxel
Iterative estimation with some stopping criterion
IPRD13 7 - 10 October 2013 Siena, Italy
Density based Clustering Algorithm
The FOF is a percolation algorithm normally used to identify dark matter halos from N-body simulations
It defines uniquely groups that contain all the particles separated by a distance smaller than a given linking length.
Once the lenght is defined, the algorithm identifies all pairs of particles which have a mutual distance smaller than the linking one and defines these as “friends”. Clusters are defined as sets of particles that are connected by one or more of the friendly relations, so that they are friends of friends.
Another parameter in FOF algorithm is the minimum number of particles Nmin, in a cluster. The aim is to reject spurious clusters, that is groups of friends who do not form persistent objects in the simulation.
Choosing Nmin sufficiently large allows to eliminate spurious clusters. In fact it is much more likely that a spurious cluster (noise) involves a small number of points and not viceversa.
IPRD13 7 - 10 October 2013 Siena, Italy
Results from the 3 algorithms
Poca Volume rendering
EM-ML Volume rendering
Clustering Volume rendering
IPRD13 7 - 10 October 2013 Siena, Italy
Tools for image processing
Intercommunication between computer resources for monitoring, data acquisition and image processing
User-friendly tools to handle image reconstruction, under development
IPRD13 7 - 10 October 2013 Siena, Italy
Demo
IPRD13 7 - 10 October 2013 Siena, Italy
On-going activity and outlook
A large area muon tomograph currently under construction after extensive R&D phase
Large number (104 ) of channels involved, with corresponding number of SiPM photosensors
New solutions exploited for channel reduction, electronic readout and data acquisition
Monitoring and image reconstruction with different algorithms and tools implemented
Construction of the first 2 (of 48) modules in progress
End of construction expected by end of 2014
IPRD13 7 - 10 October 2013 Siena, Italy
Outreach and dissemination activities
Due to the nature of the Project, also outreach activities are believed to be important:
Public meetings and colloquia targeted to students, high-school and citizen people
Posters, articles on local newspapers
Stands during public events Construction of an exhibition box
located in a public area for outreach activities
IPRD13 7 - 10 October 2013 Siena, Italy
The partners
Dept. Of Physics & Astronomy, University of Catania
INAF, Astrophysical Observatory, Catania
STMicroelectronics S.r.l. Catania
Insirio SPA
Meridionale Impianti Welding Technology
IPRD13 7 - 10 October 2013 Siena, Italy
Thank you for your attention and BUON APPETITO!
IPRD13 7 - 10 October 2013 Siena, Italy
Back-up slides
IPRD13 7 - 10 October 2013 Siena, Italy
Fake probability and efficiency EM-ML method
IPRD13 7 - 10 October 2013 Siena, Italy
Momentum filter
After cutting low momenta (< 1 GeV/c) muons
Additional prototype detector to reject low momentum muons being tested
IPRD13 7 - 10 October 2013 Siena, Italy
The Muon Portal for cosmic ray physics
Trigger on air showers
by 3-fold coincidences Muon bundles in the Portal
It is also planned to employ such detector prototype for cosmic ray studies, due to its large area (18 m2) and tracking capabilities.
GPS tagging used on both detectors to correlate events
IPRD13 7 - 10 October 2013 Siena, Italy
Muon tomography project* INFN and University of Padua
Drift chambers to track muons, similar to CMS
Momentum filter
Spatial resolution 200 μm
* S.Pesente et al, NIMA 604(2009)738
IPRD13 7 - 10 October 2013 Siena, Italy
LOS ALAMOS*
12 detection planes with drift tubes Spatial resolution 400 μm Angular resolution 2 mrad
* K.N. Borozdin et al, Nature 422(2003)277
IPRD13 7 - 10 October 2013 Siena, Italy
Muon Tomography Station Using GEM Detectors* Florida Institute of Technology, Melbourne
30x30 cm triple GEM 50 μm resolution for perpendicular tracks XY readout with 400 μm pitch
* K.Gnanvo et al, NIMA 652(2011)16