The aim of this project is to demonstrate the potential improvements that can be made in X- ray backscattering techniques to better identify illicitly smuggled material in cargo / baggage. The possibilities of this project will be achieved by combining a detailed understanding of the X-ray scattering processes and Monte-Carlo modelling with experimental results from poly- energetic X-ray sources and new high-efficiency, high-resolution CZT detectors.

Current state-of-the-art commercial X-ray backscatter cargo scanning systems make use of the increased scatter that results from low-Z (atomic number) organic materials to identify contraband items. The detectors used in current systems are only capable of measuring the intensity of scattered X-rays. However, areas of high-backscatter intensity, typically associated with contraband (drugs, tobacco, plastic explosives & currency), can be established as brighter regions in an X-ray image. This rather basic level of organic/inorganic separation is usually the only information available. To date, this has been considered sufficient to identify crates which don’t meet their manifest and require human inspection. This process creates delays and some crates are unnecessarily opened.

Working together, Manchester University and Rapiscan recently demonstrated that more information relating to the material composition of the inspected object was available within backscattered X-ray data. By measuring both the intensity and energy of the backscattered X-rays simultaneously it was possible to increase the level of material separation beyond that of simple inorganic/organic. The key aspects of this project were the unique combination of new high-resolution, high-efficiency, CZT detectors coupled with validation and comparison of the experimental measurements with theoretical simulations using the Geant IV (Monte-Carlo) code.

In this CASE project, the original setup will be scaled up to evaluate whether this approach can be a realistic option for an improved large-scale industrial cargo security screening device. A new CZT multi-detector setup will be used with higher-intensity poly-energetic X- ray sources, first with a pulsed 50-keV table-top X-ray source at The University of Manchester and later with a larger 200-keV X-ray source at Rapiscan.

Year 1: (at The University of Manchester):
At Manchester, you will undertake training and courses to fully acquaint themselves with the relevant nuclear physics and health and safety aspects. Alongside this work and for months 6-12, you will redesign the existing experimental setup to replace the standard mono- energetic source with a 50-keV poly-energetic X-ray source. New X-ray backscatter energy and intensity measurements will be taken with a range of materials of varying thicknesses.

The existing Geant IV simulation will be modified to include the new X-ray source and then validated against new experimental results.

Year 2: (12 months at Rapiscan’s Cargo Division facility in Stoke-on-Trent):
At Rapiscan, you will determine the viability of the technique for industrial applications using a poly-energetic 200-keV X-ray source. You will first characterise the 200-keV energy spectrum from the X-ray tube so it can be accurately defined in the simulation. During this time you will gain industrial experience with various types of X-ray imaging systems not possible at the University. The validated Geant IV simulation model, developed in year 1, will be modified to reflect the new geometry and higher X-ray output energy and intensity required in an industrial application. The performance of the model will be tested against more realistic cargo screening assemblies which Rapiscan uses to calibrate their existing commercial backscatter systems. These results will be used to determine the viability of the proposed technique in a commercial system.

Year 3: (at The University of Manchester):
During the first 6-8 months, you will consolidate all of the information and results obtained from the backscattering with the two X-ray sources as a function of material type and thickness. It is anticipated that this will result in a parameterisation of the number of backscattered counts required as a function of hidden material object thickness, atomic number and X-ray energy. In the latter 8-12 months, these research findings will be written up as a paper to IEEE and you would be expected to present the work at an international conference.

Year 4: (6 months at The University of Manchester):
You will spend the final 6 months at The University of Manchester to write up the PhD thesis and disseminate the final conclusions to Rapiscan systems.

PERSON SPECIFICATION :

Essential:

A first class or upper second-class degree in physics or related discipline.
Be able to work in radiation controlled and supervised areas.
An enthusiastic and well-motivated person with good written and oral communication skills.

The project will necessarily involve a working knowledge of scientific computing and programming.

Knowledge of radiation detectors / Monte-Carlo techniques would also be beneficial.