Kondo Gnanvo

Imaging of high-Z material for nuclear contraband detection with a minimal prototype of a Muon Tomography station based on GEM detectors

Muon Tomography based on the measurement of multiple scattering of atmospheric cosmic ray muons in matter is a promising technique for detecting heavily shielded high-Z radioactive materials (U, Pu) in cargo or vehicles. The technique uses the deflection of cosmic ray muons in matter to perform tomographic imaging of high-Z material inside a probed volume. A Muon Tomography Station (MTS) requires position-sensitive detectors with high spatial resolution for optimal tracking of incoming and outgoing cosmic ray muons. Micro Pattern Gaseous Detector (MPGD) technologies such as Gas Electron Multiplier (GEM) detectors are excellent candidates for this application. We have built and operated a minimal MTS prototype based on 30cm  30cm GEM detectors for probing targets with various Z values inside the MTS volume. We report the first successful detection and imaging of medium-Z and high- Z targets of small volumes (~0.03 liters) using GEM-based Muon Tomography.

Characterization of GEM detectors for application in the CMS muon detection system

The muon detection system of the Compact Muon Solenoid experiment at the CERN Large Hadron Collider is based on different technologies for muon tracking and triggering. In particular, the muon system in the endcap disks of the detector consists of Resistive Plate Chambers for triggering and Cathode Strip Chambers for tracking. At present, the endcap muon system is only partially instrumented with the very forward detector region remaining uncovered. In view of a possible future extension of the muon endcap system, we report on a feasibility study on the use of Micro-Pattern Gas Detectors, in particular Gas Electron Multipliers, for both muon triggering and tracking. Results on the construction and characterization of small triple-Gas Electron Multiplier prototype detectors are presented.

GEANT4 Simulation of a Cosmic Ray Muon Tomography System With Micro-Pattern Gas Detectors for the Detection of High-

Muon tomography (MT) based on the measurement of multiple scattering of atmospheric cosmic ray muons traversing shipping containers is a promising candidate for identifying threatening high-Z materials. Since position-sensitive detectors with high spatial resolution should be particularly suited for tracking muons in a MT application, we propose to use compact micro-pattern gas detectors, such as gas electron multipliers (GEMs), for muon tomography. We present a detailed GEANT4 simulation of a GEM-based MT station for various scenarios of threat material detection. Cosmic ray muon tracks crossing the material are reconstructed with a point-of-closest-approach algorithm to form 3-D tomographic images of the target material. We investigate acceptance, Z-discrimination capability, effects of placement of high-Z material and shielding materials inside the cargo, and detector resolution effects for such a MT station.

{\rm Z}

Muon tomography based on the measurement of multiple scattering of atmospheric cosmic ray muons is a promising technique for detecting and imaging heavily shielded high-Z nuclear materials such as enriched uranium. This technique could complement standard radiation detection portals currently deployed at international borders and ports, which are not very sensitive to heavily shielded nuclear materials. We image small targets in 3D using 2×2×2 mm3 voxels with a minimal muon tomography station prototype that tracks muons with Gas Electron Multiplier (GEM) detectors read out in 2D with x-y microstrips of 400 μm pitch. With preliminary electronics, the GEM detectors achieve a spatial resolution of 130 μm in both dimensions. With the next GEM-based prototype station we plan to probe an active volume of ∼27 liters. We present first results on reading out all 1536 microstrips of a 30×30 cm2 GEM detector for the next muon tomography prototype with final frontend electronics and DAQ system. This constitutes the first full-size implementation of the Scalable Readout System (SRS) recently developed specifically for Micropattern Gas Detectors by the RD51 collaboration. Design of the SRS and first performance results when reading out GEM detectors are presented.

Materials

At present, part of the forward RPC muon system of the CMS detector at the CERN LHC remains uninstrumented in the high-η region. An international collaboration is investigating the possibility of covering the 1.6 < |η| < 2.4 region of the muon endcaps with large-area triple-GEM detectors. Given their good spatial resolution, high rate capability, and radiation hardness, these micro-pattern gas detectors are an appealing option for simultaneously enhancing muon tracking and triggering capabilities in a future upgrade of the CMS detector. A general overview of this feasibility study will be presented. The design and construction of small (10×10 cm2) and full-size trapezoidal (1 × 0.5 m2) triple-GEM prototypes will be described. During detector assembly, different techniques for stretching the GEM foils were tested. Results from measurements with x-rays and from test beam campaigns at the CERN SPS will be shown for the small and large prototypes. Preliminary simulation studies on the expected muon reconstruction and trigger performances of this proposed upgraded muon system will be reported.

Detection and imaging of high-Z materials with a muon tomography station using GEM detectors

In view of a possible extension of the forward CMS muon detector system and future LHC luminosity upgrades, Micro-Pattern Gas Detectors (MPGDs) are an appealing technology. They can simultaneously provide precision tracking and fast trigger information, as well as sufficiently fine segmentation to cope with high particle rates in the high-eta region at LHC and its future upgrades. We report on the design and construction of a full-size prototype for the CMS endcap system, the largest Triple-GEM detector built to-date. We present details on the 3D modeling of the detector geometry, the implementation of the readout strips and electronics, and the detector assembly procedure.

Construction and performance of large-area triple-GEM prototypes for future upgrades of the CMS forward muon system

Current radiation portal monitors at sea ports and international borders that employ standard radiation detection techniques are not very sensitive to nuclear contraband that is well shielded to absorb emanating radiation. Muon Tomography (MT) based on the measurement of multiple scattering of atmospheric cosmic ray muons traversing cargo or vehicles that contain high-Z material is a promising passive interrogation technique for solving this problem. We report on the design and construction of compact Micro-Pattern Gas Detectors for a small prototype MT station. This station will employ 10 tracking stations based on 30cm × 30cm low-mass triple-GEM detectors with 2D readout. Due to the excellent spatial resolution of GEMs it is sufficient to use a gap of only a few cm between tracking stations. Together with the compact size of the GEM detectors this allows the GEM MT station to be an order of magnitude more compact than MT stations using traditional drift tubes. We present details of the production and assembly of the GEM-based tracking stations in collaboration with CERN and the RD51 collaboration as well as the design of the initial front-end electronics and readout system.

Construction of the first full-size GEM-based prototype for the CMS high-η muon system

We present results from a detailed GEANT4 simulation of a proposed Muon Tomography System that employs compact Micro Pattern Gas Detectors with high spatial resolution. A basic Point-Of-Closest-Approach algorithm is applied to reconstructed muon tracks for forming 3D tomographic images of interrogated targets. Criteria for discriminating materials by Z and discrimination power achieved by the technique for simple scenarios are discussed for different integration times. The simulation shows that Muon Tomography can clearly distinguish high-Z material from low-Z and medium-Z material. We have studied various systematic effects that affect the performance of the MT and the discrimination power. The implications of the simulation results for the planned development of a prototype MT station are discussed.

Design and construction of a first prototype Muon Tomography system with GEM detectors for the detection of nuclear contraband

In this article on Muon Tomography we report our work on the development of an intelligent pattern detection system for materials with high atomic numbers (Z) for Homeland Security application. Muons are naturally produced in the upper atmosphere by primary cosmic rays and are used as passive probes of a cargo volume. By sensing the incoming and outgoing tracks and measuring the momentum of each muon for a probed volume one may derive the scattering parameters. A statistical algorithm is being used to estimate scattering densities of the material in each unit volume (voxel) of the probed target. The article describes the algorithm and some results from our simulation experiments.

Performance expectations for a Tomography System using cosmic ray muons and micro pattern gas detectors for the detection of nuclear contraband

GEM detectors are used in high energy physics experiments given their good spatial resolution, high rate capability and radiation hardness. An international collaboration is investigating the possibility of covering the 1.6 < |?| < 2.4 region of the CMS muon endcaps with large-area triple-GEM detectors. The CMS high-? area is actually not fully instrumented, only Cathode Strip Chamber (CSC) are installed. The vacant area presents an opportunity for a detector technology able to to cope with the harsh radiation environment; these micropattern gas detectors are an appealing option to simultaneously enhance muon tracking and triggering capabilities in a future upgrade of the CMS detector. A general overview of this feasibility study is presented. Design and construction of small (10cm ? 10cm) and full-size trapezoidal (1m ? 0.5m) triple-GEM prototypes is described. Results from measurements with x-rays and from test beam campaigns at the CERN SPS is shown for the small and large prototypes. Preliminary simulation studies on the expected muon reconstruction and trigger performances of this proposed upgraded muon system are reported.