This proposal is for a studentship to develop key systems for the Square Kilometre Array (SKA), to be held jointly by the University of Oxford Dept of Physics, which is one of the leading contributors to the SKA design and specifications, and Selex Galileo, a leading European electronics company. The SKA is a project to build by far the largest radio telescope ever constructed, which will have a transformative effect on many areas of astrophysics and cosmology. The key science goals of the SKA include mapping the development of the structure of the universe by measuring the positions in time and space of a billion galaxies; testing fundamental theories of physics by precision measurements of the most extreme objects in the universe; and studying the formation of earth-like planets. In its final form, it will consist of an array of around 2000 15-m dish antennas, plus around 500 large (~200-m diameter) phased array antennas covering two different frequency bands (totalling over ten square kilomtres of physical collecting area), plus a large central data processing facility, costing a total of around E1.5 billion. The antenna arrays will be concentrated in a remote desert site, with some elements spread over continental distances. The aperture arrays will be the largest digital signal processing networks ever built, with a total input data rate of several petabits per second (greater than the entire current internet) and processing power of many peta-operations per second (comparable to all the personal computers in the UK combined). The period covered by this proposed studentship coincides with the pre-construction phase of the SKA, during which the current plans and outline designs will be converted into functional prototype sub-systems which are capable of being manufactured and installed on an industrial scale. This is therefore the ideal time to have a joint academic-industrial studentship working on a critical aspect of the SKA Phase 1 system design, the low-band aperture array. By using a phased array instead of a large dish antenna, it is possible to image a large number of independent fields of view simultaneously, vastly increasing the survey speed. Once digitized, the signals from each antenna element are broken in to narrow frequency channels, then combined heirarchically into phased beams consisting of weighted sums of all the ~10,000 antenna elements in an array station. Complex gain factors applied to each input element both calibrate out amplitude and phase imbalances in the elements, and generate well-defined beams pointing to different parts of the sky. The project student will study the detailed implementation of the RF analogue electronics, digitization, and initial signal processing of the data streams. The performance requirements for the SKA, in terms of bandwidth, data throughput and volume of output data are far greater than any currently implemented system, and will require innovative design solutions, and a close interaction between science requirements and engineering implementations. Of particular importance is that the designs must be optimized for low manufacturing cost, ease of initial testing, low power consumption, and long service life with little or no maintenance. These are areas where Selex Galileo has vast experience and will bring a major input to the system design. The precise areas of study for the student will be fixed during the initial phase of the project rather than now; the student will not start until October 2011, and the overall system design will have moved on by then, and the scope of work available is also much greater than any one student could cover in a PhD. The supervisors will agree a programme of work which makes best use of the interests and skills of the student and the capabilities of the industrial partner, with the aim of maximising the impact of the project on the SKA design and hence the UK industrial involvement in the SKA construction phase.

Vision is arguably the most important of our senses and our most direct channel of interaction with the surrounding world. It is no surprise therefore that so much of the technology that affects our everyday lives relies on light in one form or the other. The continuous strive to improve our light sources, ranging from lasers for research purposed to ambient lighting technologies is paralleled by a continuous increase in efforts to improve our imaging capabilities, ranging from artificial vision implants to hyperspectral imaging. An exciting and emerging imaging technology relies on the ability to detect remarkably low light signals, i.e. even single photons. This same technology, based for example of Single-Photon-Avalanche-Detectors (SPADs) comes hand in hand with another rather unexpected and also remarkable feature: incredibly high temporal resolution and the ability to distinguish events that are separated in time by picoseconds or less. This temporal resolution is obtained by operating the SPAD in so-called Time-Correlated-Single-Photon-Counting (TCSPC) mode, where the single photons are detected in coincidence with an external trigger and then electronically stored with a precise time-tag that, after accumulating over many events, allows to precisely identify the photon arrival time. These technologies are now relatively well established and are routinely employed in research activities, mainly associated to quantum optics measurements and time of flight measurements. However, these detectors are all single pixel detectors and thus do not allow to directly reconstruct an image in much the same way that a digital camera with a single pixel will not create an image. Workaround solutions have been adopted; for example a laser may be scanned across an object and the single pixel records intensity levels for each position of the laser beam. However, our obsession with the pixel-count in our latest digital camera clearly explains the paradigm shift in going from a single pixel detector to a multi-pixel detector and eventually to high resolution imaging. ULTRA-IMAGE aims at demonstrating a series of applications of very novel SPAD technology: for the first time these detectors are available in imaging arrays. This is an emerging technology that will represent the next revolution in imaging and we will have first hand access to each technological breakthrough in SPAD array design, as they occur over the next few years. We are currently employing 32x32 SPAD arrays and will be using the first ever (at the time of writing) 320x240 pixel array, which is able to deliver the first high quality spatially resolved images. The remarkable aspect of these detectors is that they still retain their picosecond temporal resolution therefore enabling a series of game-changing and remarkable technological applications that are not even conceivable with traditional cameras. As examples of the potential of this new imaging technology, we will utilise our SPAD cameras to visualise the propagation of light and perform time-of-flight detection of remote objects in harsh environments (the FEMTO-camera), to enable of the real-time tracking of objects hidden from view (the CORNER-camera), and to perform the first quantum measurements using low-rep rate, high-power lasers (the QUANTUM-camera). The solutions we will develop are enabled by four key features: first, the single-photon sensitivity of silicon detectors; second, the spatial resolution provided by the arrayed nature of the detectors; third, the precise picosecond and femtosecond timing resolution; and fourth, the ultra low-noise performance of gated detection.

Current developments and future trends in small-scale devices used in a variety of industries such as electronic equipment and micro-process and refrigeration systems, place an increasing demand for removing higher thermal loads from small areas. In some cases further developments are simply not possible unless the problem of providing adequate cooling is resolved. The progression from air to liquid and specifically flow boiling to transfer the high heat fluxes generated is thus the only possible way forward. Evaporative cooling can, not only transfer these loads but also offer greater temperature uniformity since the working fluid can be (in a carefully designed system) at a constant saturation temperature. The consideration of microchannel flow boiling processes has been made possible by developments in microfabrication techniques both in metals and substances such as silicon. However, there still remain fundamental fluid flow and heat transfer related questions that need to be addressed before a wider use of these micro heat exchangers is possible in industry. The specific challenges that will be researched - both fundamental and practical in nature - include flow instabilities and mal-distribution which are the result of interaction between the system manifolds and the external circuit. These can lead to flow reversal and dry-out in the heat exchanger with subsequent drastic reduction in heat transfer rates. The understanding of the fundamental physical phenomena and their relevance to industrial designs is one of the focal points and constitutes one of the major challenges of the proposed research. The effect of other parameters such as inlet sub-cooling, which again relates not only to the micro-heat exchanger itself but also to the overall design, will be addressed along with material/surface characteristics through the use of both metallic and silicon microchannels. The work proposed will include carefully contacted detailed experiments measuring relevant parameters such as local heat flux, temperature and pressure combined with flow visualization through industrially available and purposely developed and manufactured sensors. The research teams will not only develop or adapt advanced instruments for accurate measurements at these small scales but also develop new three-dimensional numerical tools capable of capturing the extremely complex physical phenomena at, for example the triple-line (vapour-liquid-solid). These techniques will not only help elucidate the current phenomena but can find wide application in similar research, both in thermal and biomedical flows. The proposal brings together two teams of academics working both in microfabrication/sensors and two-phase flow supported by industry (Thermacore, Selex Galileo, Sustainable Engine Systems and Rainford Precision) to tackle some of the key fundamental challenges that will enable a wider adoption of this cooling method hence meeting current and future needs in the industry. The proposed research will also have a wider impact on energy conservation and environmental footprint trough, for example, more efficient thermal management of data/supercomputing centres around the world that can lead to a reduction in energy consumption and reuse of heat that would otherwise be rejected.

Sensors have for a long time played a vital role in battle awareness for all our armed forces, ranging from advanced imaging technologies, such as radar and sonar to acoustic and the electronic surveillance. Sensors are the "eyes and ears" of the military providing tactical information and assisting in the identification and assessment of threats. Integral in achieving these goals is signal processing. Indeed, through modern signal processing we have seen the basic radar transformed into a highly sophisticated sensing system with waveform agility and adaptive beam patterns, capable of high resolution imaging, and the detection and discrimination of multiple moving targets. Today, the modern defence world aspires to a network of interconnected sensors providing persistent and wide area surveillance of scenes of interest. This requires the collection, dissemination and fusion of data from a range of sensors of widely varying complexity and scale - from satellite imaging to mobile phones. In order to achieve such interconnected sensing, and to avoid the dangers of data overload, it is necessary to re-examine the full signal processing chain from sensor to final decision. The need to reconcile the use of more computationally demanding algorithms and the potential massive increase in data with fundamental resource limitations, both in terms of computation and bandwidth, provides new mathematical and computational challenges. This has led in recent years to the exploration of a number of new techniques, such as, compressed sensing, adaptive sensor management and distributed processing techniques to minimize the amount of data that is acquired or transmitted through the sensor network while maximizing its relevance. While there have been a number of targeted research programs to explore these new ideas, such as the USs "Integrated Sensing and Processing" program and their "Analog to Information" program, this field is still generally in its infancy. This project will study the processing of multi-sensor systems in a coherent programme of work, from efficient sampling, through distributed data processing and fusion, to efficient implementations. Underpinning all this work, we will investigate the significant issues with implementing complex algorithms on small, lighter and lower power computing platforms. Exemplar challenges will be used throughout the project covering all major sensing domains - Radar/radio frequency, Sonar/acoustics, and electro-optics/infrared - to demonstrate the performance of the innovations we develop.

The internet data rate of Mb/s is currently available to UK homes thanks to installation of fibre network. Recently Fujitsu, a major telecom company, outlined their plan to lay Gb/s fibre network in UK, which can increase the data rate to 10 Gb/s and beyond. Therefore optical fibre will play an ever increasing importance in our life and hence there is a clear need to carry out research in ultrafast optical components such as photodiodes, used to convert optical signal to electrical signal. In photodiodes the energy from light is used to release an electron from an atom and a detectable current is generated when the electron is swept by an electric field. In a specially designed avalanche photodiode (APD) the electric field is increased such that a single electron generated by the photoelectric effect can produce an avalanche of electrons and holes. Consequently a much larger signal is produced, leading to a better signal to noise ratio. Unfortunately current commercial APD can only work up to 10 Gb/s and is therefore not future proof. In this proposal, we will develop extremely thin 10-50 nm semiconductor layer to achieve the avalanche effect at ps time scale such that our APDs can operate at bit rates of Tb/s. The new semiconductor materials that will be developed in this project are AlAsSb and AlGaPSb since they have great potential to withstand extremely high electric field while maintaining low dark current (essential to minimise errors in digital signal). Crucially since our materials are only nm thick, we can engineer the electric field in APD to impose some degree of coherence in the electron and hole behaviours so that the avalanche effect occurs with minimal noise. We believe our APDs can be designed to approach the performance of an ideal noiseless APD with high bandwidth for optical communications. We recently demonstrated that the avalanche effect in thin AlAsSb is relatively immune to temperature change. Therefore in addition to ultra high speed optical communication, our proposed nm scaled AlAsSb and AlGaPSb avalanche layers are envisaged to work as an ultra fast photon counter with high immunity to ambient temperature fluctuation. Since a photon is the basic unit of light, the "ultimate" light sensor is achieved by increasing the avalanche gain to approximately a million so that the APD works as a photon counter. Our thin avalanche layer has the potential to register a photon count in a few ps, which is at least an order of magnitude faster than current APD photon counters. If successful one of the major impacts of our photon counter will be to improve the data encryption technique called quantum key distribution in which the data is encrypted using a single photon. This is believed to be the most secure encryption technology. Any unauthorised detection of the photon will cause a significant error rate, and hence alerting the sender of the attempted hacking. Therefore the high thermal stability and fast response time of our APDs will enhance the robustness of future quantum cryptography systems. We also believe our new technology will bring significant improvement to medical X-ray imaging as the APD can improve the signal to noise ratio of X-ray detection system. Typically the avalanche effect increases the electrical signal, induced by the X-ray absorption, to above the electronic circuit noise and hence enhancing the image quality. Our recent work showed that having a thin avalanche layer is essential for high performance X-ray APD. Hence our work will enable a new generation of X-ray APDs for imaging applications. To achieve the goals discussed above we will carry out very systematic development of AlAsSb and AlGaPSb APDs via advanced growth of the semiconductor crystals and optimised chemical etching process as well as meticulous measurements to extract key material properties for design of high performance APDs utilising nm avalanche regions.