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.

Understanding how the structure and physical properties of materials change under extremes of pressure and temperature is essential if we are to develop predictive capabilities on how materials work under such conditions, thereby driving innovation in material design and engineering for the improved materials of tomorrow. Much progress has been made in the last 20 years, to the extent that our understanding of how the crystallographic and electronic structure of matter changes when it is compressed to very high pressures has transformed completely in that time. However, the lack of suitable technologies has severely limited our ability to tackle two key "known unknowns": how do pressure-induced structural changes occur in elements, and how are the microstructure and physical properties of more complex materials, such as key binary alloys, affected by extreme pressures and temperatures. We will exploit our team's expertise in experimental high-pressure physics, combined with recent advances in high repetition rate lasers, and the unprecedented brightness and spatial coherence of next generation synchrotron and x-ray free electron laser facilities, to make definitive studies of phase transitions, transition mechanisms, microstructure, and material strength in key elemental and alloy systems using x-ray diffraction and imaging. In collaboration with our Project Partners, we will then use electronic structure calculations to understand the physics behind the observed material response, and thereby develop new understanding and improved predictive capabilities in the behaviour of matter at extreme conditions.

1. The purpose of the project Development and commercialization of imaging detectors using artificial diamond technology to provide greatly enhanced performance. 2. Introduction The need to detect fast signals is crucial in many disciplines. Very high speed, low amplitude light signals need signal amplification. The photomultiplier tube (PMT) was the first device to use electronic signal amplification in a vacuum tube for optical light and has been a workhorse detector since. Though silicon chips have replaced vacuum tubes as the technology of choice in most imaging applications they have limited high speed and sensitivity performance compared with devices such as the PMT. The aim of this project is to apply detector technology and know-how from the Space Research Centre (SRC), Leicester, developed through space science R & D, together with recent developments in diamond chemistry at the Diamond Group, Bristol, to the commercialization of an imaging PMT with ground-breaking performance for widespread commercial application and specific relevance to the defence sector / fusion plasma diagnostics at the Atomic Weapons Establishment, Aldermaston. 3. Advantages of Diamond as an electron amplification material a) High gain: Diamond is one of a small number of materials which has high electron gain when correctly treated. b) Simplified design: Diamond can have a higher gain per amplification stage, resulting in a lower number of stages being required for a given gain. c) Enhanced timing: The amplification properties of diamond allow improved signal timing and reduced background. d) Lower gain variability: The higher gain of diamond reduces the variability in the gain. e) Low noise: Diamond is less susceptible to thermal noise so it can operate with lower noise levels or at higher temperatures. f) Large area: Synthetic diamond offers low cost, large area coating and is easily grown on shaped surfaces. g) Stability: Synthetic diamond has a stable performance over long periods. Its performance remains high after exposure to air. The electron gain properties of synthetic diamond promises to greatly expand the usage of PMTs in many fields. 4. Application of synthetic Diamond to Detectors We have already measured the performance of synthetic diamond and our measured data supports published results and demonstrates the potential benefits of synthetic diamond as a detector material. This project will transfer the technology from proof-of-concept to prototype, beginning with optimization of manufacturing processes. Firstly we will manufacture two demonstrator detectors to provide data on process optimization. The next stage of the project will be development of a single transmissive gain stage. Transmissive dynodes can operate in two modes: - a) Transmission: input electrons enter through one surface of a thin film of diamond, and output electrons exit through the other. b) Refection: diamond is deposited on an open conductive wire mesh. Input and output electrons enter and exit through the same diamond surface. The transmission technique is superior, providing better detector performance, but is more demanding because of the need to produce very thin films, however we have already demonstrated manufacture. We will investigate both techniques and choose the optimum technology based on performance, manufacturability, developmental and manufacturing costs, and development timescale. We will initially demonstrate a single stage transmissive gain stage to provide comprehensive device diagnostics. The final stage of the project is to design, build and demonstrate a detector using a stack of gain stages with fast response and high gain and incorporating an imaging capability. Performance evaluation will involve testing with AWE collaborators at Aldermaston and field trials in a laser fusion facility at Los Alamos, and in photon counting mode at Photek and SRC.

The invention of the laser in the early 1960s led to experiments where high power (> million Watts) infra-red and visible pulsed lasers were focused onto solid targets in order to produce hot (> 0.5 million degrees Kelvin) plasmas. In almost 50 years of study, the physics of the laser interaction, the physics of the expanding plume and many important applications have been elucidated in some detail. When focussed onto solid targets, visible/infra-red lasers do not penetrate to the solid for most of the pulse duration, but are absorbed in the expanding plasma plume at densities 100- 1000 times smaller than the solid density. Dropping the laser wavelength into the extreme ultra-violet (EUV), however, enables the laser to penetrate into the solid and to create plasma directly at the solid density. Initial modelling studies that have been undertaken by the PI show that the interaction of EUV laser radiation with most solid targets will cause a rapid drop in opacity (so that the target 'bleaches'). Initially an attenuation length for the EUV photon energy is bleached and then another attenuation length, so that a 'bleaching wave' propagates through the solid target on a sub-nanosecond timescale. A much more massive amount of target material is effectively ablated than can occur with infra-red or visible radiation of the same pulse energy and focal spot diameter. Little modelling work has been undertaken to elucidate understanding of EUV laser-produced plasmas because of the lack of sufficiently energetic (> 10 microJoules) laboratory EUV lasers for experiments. However, reliable capillary discharge lasers operating at wavelength 46.9 nm (photon energy 26.4 eV) producing up to 1 milliJoule/pulse and peak powers of a million Watts have been developed at the Colorado State University (CSU). We propose to develop simulation models to interpret emission spectra and mass spectrometer results from EUV laser produced plasmas. We will test spectrometer diagnostics using the University of York high power infra-red laser and in collaboration with CSU make spectral and mass spectrometer measurements for comparison to the simulation models. A new class of laser-produced plasma will be studied with potential impact in the study of warm dense matter, laser cutting and ablation and solid material lithography with relevance to the $70B p.a. revenue industry associated with the manufacture of microelectromechanical systems (MEMS).