Material Identification with Cosmic Ray Muons using RPCs

Abstract

A: We plan to build an imaging setup for material identification utilizing the Coulomb scattering of cosmic ray muons due to their interaction with the materials and tracking their trajectories with Resistive Plate Chambers (RPCs). To begin with, we consider a setup of six RPCs stacked in a parallel manner to read the position and timing information of the muons before and after their interaction with a phantom of a given material using a set of three RPCs for each phase. Here we present a simulation work carried out to study the image formation of phantoms of several materials. A detailed modeling of the imaging system consisting of six RPCs was done using GEANT4. Cosmic Ray Library (CRY) was used for generation of particles with the appropriate energy and zenith angle distribution. Three reconstruction algorithms were followed for material identification and image reconstruction, viz. Point of Closest Approach (POCA), Iterative POCA and the Binned Cluster Algorithm. A weighted metric discriminator was calculated for target object identification. Using the algorithms, the imaging of the Region of Interest (ROI) lying between the two layers of RPCs was done. The time required to discriminate target objects and do the image reconstruction has been studied.

Momentum-Dependent Cosmic Ray Muon Computed Tomography Using a Fieldable Muon Spectrometer

“…Minimizing the number of muons provides substantial time savings but can worsen the image quality, whereas a higher number of measured muons can improve image contrast and resolution but also increases measurement time. Recent efforts have shown that muons in the order of millions are required for imaging large-scale objects such as shipping containers [17,22,23] or dry casks [19,24,25]. This translates to measurement time in the order of hours or even days, depending on the detector characteristics, i.e., size and orientation.…”

Muon tomography using cosmic-ray muons

“…Eventually, the scattering angle can be determined from the reconstructed incident and scattered trajectories. We have proposed such a setup and studied its performance by producing numerical images based on the scattering of muons in the test objects followed by their analysis using statistical process and an image processing technique based on Pattern Recognition Method (PRM) [3]. Afterwards, the simulation framework has been used to investigate the efficacy of the setup in detecting a few cases of defects commonly found in civil structures [4].…”

“…The same algorithm assesses the clustering of scattering vertices through calculation of a weighted metric distance which is used for material discrimination. It has been found that the BCA algorithm is able to differentiate high and low-Z materials, like air and lead, with half an hour exposure while more exposure (at least one hour) is needed to differentiate between two closely lying high-Z materials, like lead and uranium [3]. Taking the momenta information of the muons into account along with improved spatial resolution and larger area coverage of the detector in the setup, the BCA can be useful in material discrimination in shorter time.…”

“…The performance of the proposed MST setup in segregating different materials has been evaluated by determining statistical significance using tstatistics. It has been noted from the results of the analysis that the data with spatial resolution of 200 and 500 micron are not significantly differentiable from the ideal resolution as the null hypothesis could not be rejected for these two cases [3]. Eventually, the numerical investigation of the civil cases has been carried out with 200 micron resolution.…”

Material Discrimination in Cosmic Muon Imaging using Pattern Recognition Method

“…The fitting of the tracks and determining the scattering vertices have been done using Binned Clustering Algorithm (BCA) [7] followed by calculation of the angle. The description of the process is also available in another report of the authors where a separate method of material discrimination has been adopted [8]. The tracks with scattering angle below a certain threshold value have been rejected, which are mostly due to particles which cross the ROI, yet don't pass through any target object (un-scattered muons) and high-energy muon which scatter feebly.…”