Detection and Imaging of High-Z Materials with a Muon Tomography Station Using GEM Detectors

TL;DR

This paper presents a new muon tomography station using GEM detectors for high-resolution 3D imaging of high-Z materials, demonstrating promising initial results for detecting shielded nuclear threats.

Contribution

It introduces a full-size GEM-based muon tomography prototype with advanced readout electronics and demonstrates the first implementation of the SRS for Micropattern Gas Detectors.

Findings

GEM detectors achieved 130 micron spatial resolution.

First full-size SRS implementation for GEM detectors.

Preliminary imaging results show potential for detecting shielded nuclear materials.

Abstract

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 $2\times 2 \times 2 mm^3$ 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 micron pitch. With preliminary electronics, the GEM detectors achieve a spatial resolution of 130 microns 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 $30 \times 30 cm^2$ 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.