Detection and Imaging of High-Z Materials with a Muon Tomography Station using GEM Detectors Test Targets K. Gnanvo

1

, W. Bittner

1

, B. Benson

1

, F. Costa

2

, L. Grasso

1

, M. Hohlmann

1

, J.B. Locke

1

, S. Martoiu

2

, H. Muller

2

, M. Staib

1 1

Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, FL, USA

2

CERN, Geneva CH 1211, Switzerland

Abstract

Muon Tomography based on the measurement of multiple scattering of atmospheric cosmic ray muons is a promising technique for detecting heavily shielded high-Z nuclear materials such as enriched uranium. It uses the multiple scattering of cosmic ray muons by matter to produce a 3D tomographic image of materials with sensitivity to atomic number Z and mass density of the material. In the future, muon tomography could well complement standard radiation detection portals currently deployed at international borders and ports, which are not very sensitive to heavily shielded nuclear materials. We have operated a first minimal prototype for a Muon Tomography station that employs Gas Electron Multiplier (GEM) detectors for muon tracking. We present experimental results on the spatial resolution achieved with the GEMS and on tomographic imaging of three materials. With the next prototype MT station we will probe an active volume of ~27 liters. We discuss the basic performance of the GEM detectors when read out with the final electronics. This represents the first full-size implementation of the Scalable Readout System (SRS) recently developed specifically for Micro-Pattern Gas Detectors by the RD51 collaboration. Design and performance of the SRS for this muon tomography application are presented.

Muon Tomography (MT) Principle

Minimal MT station with preliminary FE electronics:

 4 Triple-GEMs equipped with a total of 8 Gassiplex FE cards  Readout of limited area of 5×5 cm 2 for each Triple-GEM  Targets of different Z-values at the center of the MT volume

Initial DAQ system:

 VME crate: Caen V551, V550 CRAMS 10-bit ADC  NIM crate for HV and LV power  LabView online DAQ software

Minimal MT Station

target Top GEM 0

Results from Minimal MT Station

3D Imaging of Targets

Fe data 925 ev.

Pb data 1215 ev.

Residual Analysis: 130



m Spatial Resolution

Scalable Readout System (RD51, CERN)

• • • • •

General Framework:

Small system needs only a few channels/chips; low-cost readout Large systems can use the same readout but with a much larger number of on-detector chip hybrids and FE cards FE adapter cards integrate into SRS with application-specific logic HDMI cables link hybrids on the detector with the readout Default online DAQ system is DATE (DAQ of ALICE exp.) running on an SLC4 PC with AMORE for data quality monitoring.

DAQ PC: DATE+AMORE Ta data 1671 ev.

Ta MC

Triple-GEM Readout with the SRS

Triple-GEM w/ 12 Hybrids

30cm × 30cm (1536 strips)

M S

APV25 Hybrid (128 ch.) ADC / FEC DATE Run Control GUI

Panasonic connector Diode protection Bonded APV25 chip HDMI connector Slave card connector

SRS uses DAQ software of ALICE exp. at LHC: - DATE + Gb Ethernet: DAQ & Event builder - AMORE: Online monitoring & offline analysis

chip hybrid 12bit-ADC & Front End Concentrator cards

First Results from SRS data

raw data

APV25 raw data

decoded raw data 1 time bin

Typical 2D Muon Hit on Triple-GEM

Y-Strip Cluster X-Strip Cluster X-Strip Number Y-Strip Number

Cosmic Data Run with 5 Triple-GEMs

We individually recorded pedestal and data runs with cosmics for five triple-GEM detectors with a total of 20k events in each run.

We triggered the SRS with the coincidence signal of a pair of 40×50 cm 2 plastic scintillators at a rate of 10Hz. The event size without zero-suppression is currently 60kB. The cosmic data events are found to have an average strip cluster size of about 7 strips. The signals from the APV25 hybrids are sampled at a frequency of 40MHz, which allows the hybrid to store up to 30 sampled time slices when operating in multi-peak mode. We apply a baseline correction to the data for each event and for each time bin before subtracting the pedestal offsets. From the pedestal widths, the average noise level is estimated to be ~20 ADC counts (12 bit ADC range).

Acknowledgments & Disclaimer

We thank Leszek Ropelewski (GDD, CERN), Maxim Titov (CEA, Saclay), Pierre van de Vyvre, Barthelemy Von Haller, and Adriana Telesca (ALICE DAQ, CERN) for their help and technical support with the detector construction and data acquisition systems at CERN. This material is based upon work supported in part by the U.S. Department of Homeland Security under Grant Award Number 2007-DN-077-ER0006-02. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Department of Homeland Security.