Search for hidden high-Z materials inside containers with ... · Search for hidden high-Z materials inside containers with ... GPS tagging of the events for possible correlation

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


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


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


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


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)


Muon Tomography

L. Schultz IEEE NSS Conference Record (2006)

l


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


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,…)


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


Mechanical structure

Mechanical structure under control with PLC Monitoring and storage of various parameters Sensors for alignment and alarms

Assembly tools


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


Various designs of extruded strips tested and simulated by GEANT4

Strip design

Threshold 2 p.e.

Threshold 1 p.e.


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)


Basic SiPM characterization


The SiPM test station @ INAF in Catania

fotodiodo


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


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


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


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


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


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


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


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


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.


Results from the 3 algorithms

Poca Volume rendering

EM-ML Volume rendering

Clustering Volume rendering


Tools for image processing

Intercommunication between computer resources for monitoring, data acquisition and image processing

User-friendly tools to handle image reconstruction, under development


Demo


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


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


The partners

Dept. Of Physics & Astronomy, University of Catania

INAF, Astrophysical Observatory, Catania

STMicroelectronics S.r.l. Catania

Insirio SPA

Meridionale Impianti Welding Technology


Thank you for your attention and BUON APPETITO!


Back-up slides


Fake probability and efficiency EM-ML method


Momentum filter

After cutting low momenta (< 1 GeV/c) muons

Additional prototype detector to reject low momentum muons being tested


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


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


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


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

http://research.fit.edu/hep_labA/FIT_Scenario_Video_NoDet.avi

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Search for hidden high-Z materials inside containers with ... · Search for hidden high-Z materials inside containers with ... GPS tagging of the events for possible correlation