The University of Bristol and the Atomic Weapons Establishment (AWE) aim to produce high resolution resistive plate chambers (HRP) for cosmic ray muon tomography. Cosmic ray muons can be used to non-invasively probe luggage and other containers. Muons are impossible to screen against and as no above-background radiation is introduced, it is impossible to booby-trap a device such that it explodes during examination. HRPCs are ideal to detect the muons as they are cheap and straight-forward to build, even for large areas and do not require an external trigger. This device can be used e.g. to screen containers and luggage and will be used in ports and airports.

National nuclear security is currently a hot topic in light of terrorist attacks on Western cities in recent years. The fear that a non-state actor with malicious intent could commence a nuclear attack on our nation is real. To stop these materials entering the UK, the plan is to scan all cars and cargo containers. The best technique for scanning is cosmic ray tomography (CRT). This is because cosmic muons are highly penetrating, are naturally occurring and have a high rate. This means that it is impossible to screen against and since no above-background radiation is introduced one cannot trigger the device during the scan. Starting November 2009 we have successfully built a Cosmic Ray Tomography system based on high resolution resistive plate chambers. This mini-PIPPS project has been very successful. Now that the feasibility study is complete, we need to make the next step and study the main issues for producing an RPC system suitable for commercial exploitation. The main issues to make that next step are: the maximum strip length, reduction of the number of read out channels and sealing the RPCs. In this project we focus on the reduction of readout chips. To reduce their number we will study the potential of capacitively coupled floating strips. These strips are not connected to the readout chips, but share their charge with their neighbors until the charge is shared with a neighbor that is connected to the readout chip. This is a well-known "trick" in silicon detectors and we want to study the potential for our detector systems. This will make RPC-based systems significantly cheaper to build. Completion of this proposal will allow our collaboration to commercially exploit STFC developed technology for the benefit of UK industry.

At ambient conditions, the light alkali metals Li, Na and K are nearly free electron (NFE) metals. But rather than becoming MORE free-electron like when compressed, these metals undergo transitions to unusual and complex structural and electronic forms as a result of density-driven changes in the interactions of the ions and electrons. While such behaviour is expected in all high-density matter, the physics is most evident in the alkali metals due to their NFE behaviour at ambient conditions, and their very high compressibilities. They thus offer a unique insight into the behaviour of all other metals at very high densities. We will exploit our team's expertise in experimental high-pressure physics to create solid and fluid alkali metals at unprecedented densities, and then determine their structural behaviour using x-ray diffraction techniques at synchrotrons, x-ray free electron lasers, and high-energy laser facilities. We will then use electronic structure and quantum-molecular-dynamics calculations to understand the physics behind the observed behaviour, and thereby develop new understanding and improved predictive capabilities in the behaviour of matter at ultra-high densities.

The aim of the project is to develop a new generation of radiation hard fast neutron detectors using SiC, and to assess their performance as a gamma-blind fast neutron detector in high flux photonuclear reactions. This work is collaboration with the Threat Reduction Department at AWE, and aims to transfer a new detector technology from the University which is optimsed for use in their photonuclear material interrogation programmes. The projecrt benefits from the existing STFC funded detector R&D at Surrey for radiation hard heavy ion detectors (eg. diamond) for nuclear physics experiments at GSI. Photonuclear material interrogation is a promising method for future threat reduction programmes. Here we propose to develop a new fast neutron detector based on the compound semiconductor SiC. The unique properties of SiC combine room temperature operation, extreme radiation hardness, high neutron sensitivity, and gamma-blind performance. It is therefore ideal for neutron detection in high-flux mixed n/gamma fields. In 2008 a break through in SiC material quality from Cree Inc has now made available free-standing wafers of electronic grade SiC, of the quality required for radiation detectors. We propose to fabricate prototype SiC detectors at Surrey's detector laboratories, and then test their performance at AWE and NRL test facilities. Various active interrogation methods for threat reduction and SNM detection are currently being developed, including nuclear resonance fluorescence and active neutron interrogation. In such cases, the ability to accurately measure the neutron fluence emitted from a test object is crucial, often in the presence of a strong mixed neutron-gamma field. In particular, the use of a pulsed neutron beam to create prompt neutron activation (PNA) is a promising technique for the interrogation of shielded SNM. In this technique, short neutron bursts of duration 100-200 us are used to generate fast fission neutrons from the interrogated material. The presence of lead, cadmium or hydrogenous shielding materials around the SNM produced short decay times for the emitted neutrons, due to their thermalisation and capture. Therefore the success of the PNA technique requires use of neutron detectors that have a rapid response and are sensitive during the period immediately after each incident neutron burst. Prototype SiC detectors have recently been demonstrated as a compact semiconductor-based fast neutron detector. In general, semiconductor-based neutron detectors should fullfill the following criteria: - High sensitivity to fast neutrons, with gamma-blind selectivity to reject photon events. - Compact detectors capable of operating at room temperature, with the potential to scale-up to large active areas. - Radiation hard detectors which are capable of withstanding significant neutron/gamma dose. SiC offer particular advantages over silicon detectors, principally in its superior radiation hardness, and its ability to operate in extreme environments at eleavated temperatures. Direct funding from AWE's (value ~£30k) has been approved to support the CASE partner activities within this project. This money will cover the additional CASE student stipend plus plus the provision of consumables for the project (mainly purchase of SiC wafers). The student will spend approximately 1 week per month at AWE, and will establish a collaborative partnership between the Threat Reduction group at AWE and the Detector Physics group at Surrey.

The proposed research programme concerns the development of multiscale methods based on the coupling of continuum and molecular dynamics. Multiscale methods aim to enable the simulation of complex problems such as the study of interfacial friction in materials subjected to shock waves, as well as to provide a meso scale modelling strategy for the range of length and time scales, where molecular methods are computationally expensive and continuum methods are not sufficiently accurate. The research programme includes the development of hybrid solution interface (HSI) for coupling multiscale domains; a dynamic-feedback coupling (DFC) strategy; implementation of constitutive equation to account for the elastic-plastic behaviour in the stress-tensor calculation; verification and validation studies; and computational studies of interfacial dynamics phenomena under shock wave conditions. The verification and validation studies include comparisons of the multiscale methods against previous molecular dynamic simulations for sliding interfaces and experimental data from HE-driven dynamic-friction experiments provided by AWE. Both small and large scale simulations of shock wave propagation and sliding interfaces will be carried out to gain insight into: (i) fracture and breaking of small parts of the surface; (ii) change of the geometrical shape of the surface or interface; (iii) melting and formation of a liquid layer; (iv) solidification of temporarily liquefied parts of the surface; (v) structural changes in the materials.