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Grant
Agency: GTR | Branch: EPSRC | Program: | Phase: Research Grant | Award Amount: 72.24K | Year: 2016

We propose an ambitious multi-institution experimental programme to investigate one of the greatest mysteries in astrophysics: the acceleration mechanism that leads to generation of high energy cosmic rays. The presence of energetic particles in the Universe is a well established fact, with measurements of the cosmic ray (CR) spectrum extending up to astonishing 1e20 eV. In spite of this, the exact mechanism that leads to such high energy particles still remains controversial. The central theme of this proposal is to conduct a programme of linked earth-based experimental and theoretical investigations into CR acceleration mechanisms to address this long running problem. Although many different processes may result in CR acceleration, the present day understanding is that shock waves and turbulence play an essential role in energizing both the electrons and ions present in the interstellar medium. We will perform linked experimental and numerical studies of the acceleration of electrons in strong shocks formed in magnetised plasmas. The shocks will be formed by supersonic plasma flows created by high intensity lasers and Mega-Ampere-level pulsed currents. The first set of experiments will investigate the initial acceleration of electrons, which should allow the formation of electron population with energies significantly exceeding their initial thermal energy. This is expected to occur due to plasma wave turbulence which is excited in the pre-shock plasma by the ions reflected from the shock front, but this mechanism has never been tested by experiment. We will characterise the development of the turbulence and measure the parameters of the accelerated electrons using state-of-the-art diagnostic techniques previously developed by us. In the second set of experiments, we will investigate the so-called diffusive shock acceleration mechanism, which is considered as the most plausible mechanism of cosmic ray acceleration. This will be achieved by injecting sufficiently energetic electrons into the shock, in such a way that these electrons will then sample both the pre- and post-shock regions, performing multiple passages through the shock front as required for this mechanism to operate efficiently. Use of a magnetic spectrometer will allow direct measurements of the energy of the accelerated electrons which will be compared with theoretical predictions. As part of this project we will also perform numerical simulations using state of the art hybrid-MHD and PIC codes and cross-compare the results with our experimental data. The computational and theoretical components of the project will allow us to forge a strong connection between experiment, astrophysical models and observations. The proposed research lies at the border between Plasma Physics and Astrophysics, and will advance the development of the novel research area of Laboratory Astrophysics, which seeks to enhance the understanding of the physics governing the behaviour of astrophysical objects directly via scaled laboratory experiments, combined with computer modelling. Creating the extreme plasma conditions required for scaled reconstruction of astrophysical environments in the laboratory, became possible only recently thanks to the advent of high energy lasers and fast rise-time high-current pulsed power facilities. The similarity between the lab and nature in terms of key dimensionless parameters (e.g. Mach number) is sufficiently close to make such experiments highly relevant. The timeliness of this proposal is also underlined by the growing interest in this field internationally with major efforts in USA (Rochester, Livermore - NIF) and Europe (Bordeaux - LaserMegajoule). The combined expertise of the authors of this proposal and the involvement of international collaborators from Astrophysics community will allow us to create and exploit an unprecedented capability for the Laboratory Astrophysics research and provide both breadth and depth to the programme.


Grant
Agency: GTR | Branch: EPSRC | Program: | Phase: Research Grant | Award Amount: 605.74K | Year: 2015

The project Compressive Imaging in Radio Interferometry (CIRI) aims to bring new advances for interferometric imaging with next-generation radio telescopes, together with theoretical and algorithmic evolutions in generic compressive imaging. Radio Interferometry (RI) allows observations of the sky at otherwise inaccessible angular resolutions and sensitivities, providing unique information for astrophysics and cosmology. New telescopes are being designed, such as the Square Kilometer Array (SKA), whose science goals range from astrobiology and strong field gravity, to the probe of early epochs in the Universe when the first stars formed. These instruments will target orders of magnitudes of improvement in resolution and sensitivity. In this context, they will have to cope with extremely large data sets. Associated imaging techniques thus literally need to be re-invented over the next few years. The emerging theory of compressive sampling (CS) represents a significant evolution in sampling theory. It demonstrates that signals with sparse representations may be recovered from sub-Nyquist sampling through adequate iterative algorithms. CIRI will build on the theoretical and algorithmic versatility of CS and leverage new advanced sparsity and sampling concepts to define, from acquisition to reconstruction, next-generation CS techniques for ultra-high resolution wide-band RI imaging and calibration techniques. The new techniques, and the associated fast algorithms capable of handling extremely large data sets on multi-core computing architectures, will be validated on simulated and real data. Astronomical imaging is not only a target, but also an essential means to trigger novel generic developments in signal processing. CIRI indeed aims to provide significant advances for compressive imaging thereby reinforcing the CS revolution, which finds applications all over science and technology, in particular in biomedical imaging. CIRI is thus expected to impact science, economy, and society by developing new imaging technologies essential to support forthcoming challenges in astronomy, and by delivering a new class of compressive imaging algorithms that can in turn be transferred to many applications, starting with biomedical imaging.


News Article
Site: http://phys.org/physics-news/

"EuPRAXIA will define the missing step towards a new generation of plasma accelerators with the potential for dramatically reduced size and cost," said EuPRAXIA coordinator Ralph Assmann from DESY. "It will ensure that Europe is kept at the forefront of accelerator-based science and applications." The EuPRAXIA consortium includes 16 laboratories and universities from five EU member states. In addition, it includes 18 associated partners from eight countries, involving leading institutes in the EU, Japan, China and the United States. Particle accelerators have evolved over the last 90 years into powerful and versatile machines for discoveries and applications. Today some 30,000 accelerators are operated around the world, among those some of the largest machines built by human mankind. A new technology for particle acceleration has emerged and has demonstrated accelerating fields a thousand times beyond those presently used: Plasma acceleration uses electrically charged plasmas, generated by strong lasers, instead of the usual radio frequency used in conventional accelerators, to boost particles like electrons to high energies. By the end of 2019, EuPRAXIA will produce a conceptual design report for the worldwide first five Giga-Electronvolts plasma-based accelerator with industrial beam quality and dedicated user areas. EuPRAXIA is the required intermediate step between proof-of-principle experiments and versatile ultra-compact accelerators for industry, medicine or science, e.g. at the energy frontier of particle physics as a plasma linear collider. The study will design accelerator technology, laser systems and feedbacks for improving the quality of plasma-accelerated electron beams. Two user areas will be developed for a novel free-electron laser, high-energy physics and other applications. An implementation model will be proposed, including a comparative study of possible sites in Europe, a cost estimate and a model for distributed construction but installation at one central site. As a new large research infrastructure, EuPRAXIA would place Europe at the forefront of the development of novel accelerators driven by the world's most powerful lasers from European industry in the 2020's. The EuPRAXIA consortium has the following participants: Centre National de la Recherche Scientifique (CNRS), Commissariat à l'Énergie Atomique et aux énergies alternatives (CEA) and Synchrotron SOLEIL from France, DESY and the University of Hamburg from Germany, Istituto Nazionale di Fisica Nucleare (INFN), Consiglio Nazionale delle Ricerche (CNR), Agenzia nazionale per le nuove tecnologie, l'energia e lo sviluppo economico sostenible (ENEA) and Sapienza Universita di Roma from Italy and Instituto Superior Técnico (IST) from Portugal, Science & Technology Facilities Council (STFC), University of Manchester, University of Liverpool, University of Oxford, University of Strathclyde and Imperial College London from the UK. Associated partners are: Jiaotong University Shanghai and Tsingua University Beijing from China, Extreme Light Infrastructures - Beams (ELI-B) in Czech Republic, University of Lille in France, High Energy Accelerator Research Organization (KEK), Kansai Photon Science Institute, Japan Atomic Energy Agency, Osaka University and RIKEN Spring-8 Center from Japan, Helmholtz-Institut Jena, Helmholtz-Zentrum Dresden-Rossendorf and Ludwig-Maximillians-Universität München from Germany, Wigner Research Center of the Hungarian Academy of Science in Hungary, University of Lund in Sweden, European Organization for Nuclear Research (CERN) in Switzerland, Center for Accelerator Science and Education at Stony Brook University & Brookhaven National Laboratory (BNL), Lawrence Berkeley National Laboratory (LBNL), SLAC National Accelerator Laboratory and University of California at Los Angeles (UCLA) in the U.S.


News Article
Site: http://phys.org/space-news/

In June 2015, a black hole called V404 Cygni underwent dramatic brightening for about two weeks, as it devoured material that it had stripped off an orbiting companion star. V404 Cygni, which is about 7,800 light years from Earth, was the first definitive black hole to be identified in our Galaxy and can appear extremely bright when it is actively devouring material. In a new study published in the journal Monthly Notices of the Royal Astronomical Society, an international team of astronomers, led by the University of Southampton, report that the black hole emitted dazzling red flashes lasting just fractions of a second, as it blasted out material that it could not swallow. The astronomers associated the red colour with fast-moving jets of matter that were ejected from close to the black hole. These observations provide new insights into the formation of such jets and extreme black hole phenomena. Lead author of the study Dr Poshak Gandhi, Associate Professor and STFC Ernest Rutherford Fellow in the University of Southampton's Astronomy Group, comments: "The very high speed tells us that the region where this red light is being emitted must be very compact. Piecing together clues about the colour, speed, and the power of these flashes, we conclude that this light is being emitted from the base of the black hole jet. The origin of these jets is still unknown, although strong magnetic fields are suspected to play a role. "Furthermore, these red flashes were found to be strongest at the peak of the black hole's feeding frenzy. We speculate that when the black hole was being rapidly force-fed by its companion orbiting star, it reacted violently by spewing out some of the material as a fast-moving jet. The duration of these flashing episodes could be related to the switching on and off of the jet, seen for the first time in detail." Due to the unpredictable nature and rarity of these bright black hole 'outbursts', astronomers have very little time to react. For example, V404 Cygni last erupted back in 1989. V404 Cygni was exceptionally bright in June 2015 and provided an excellent opportunity for such work. In fact, this was one of the brightest black hole outbursts in recent years. But most outbursts are far dimmer, making them difficult to study. Each flash was blindingly intense, equivalent to the power output of about 1,000 Suns. And some of the flashes were shorter than 1/40th of a second—about ten times faster than the duration of a typical blink of an eye. Such observations require novel technology, so astronomers used the ULTRACAM fast imaging camera mounted on the William Herschel Telescope in La Palma, on the Canary Islands. Professor Vik Dhillon, of the University of Sheffield and co-creator of ULTRACAM, said: "ULTRACAM is unique in that it can operate at very high speed, capturing high frame-rate 'movies' of astronomical targets, in three colours simultaneously. This allowed us to ascertain the red colour of these flashes of light from V404 Cygni." Dr Gandhi concluded: "The 2015 event has greatly motivated astronomers to coordinate worldwide efforts to observe future outbursts. Their short durations, and strong emissions across the entire electromagnetic spectrum, require close communication, sharing of data, and collaborative efforts amongst astronomers. These observations can be a real challenge, especially when attempting simultaneous observations from ground-based telescopes and space satellites." Explore further: Monster black hole wakes up after 26 years More information: Furiously Fast and Red: Sub-second Optical Flaring in V404 Cyg during the 2015 Outburst Peak. MNRAS Advance Access published March 14, 2016. www.ras.org.uk/images/stories/press/Black_Holes/mnras.stw571.full.pdf


Grant
Agency: GTR | Branch: EPSRC | Program: | Phase: Research Grant | Award Amount: 585.81K | Year: 2016

We propose an ambitious multi-institution experimental programme to investigate one of the greatest mysteries in astrophysics: the acceleration mechanism that leads to generation of high energy cosmic rays. The presence of energetic particles in the Universe is a well established fact, with measurements of the cosmic ray (CR) spectrum extending up to astonishing 1e20 eV. In spite of this, the exact mechanism that leads to such high energy particles still remains controversial. The central theme of this proposal is to conduct a programme of linked earth-based experimental and theoretical investigations into CR acceleration mechanisms to address this long running problem. Although many different processes may result in CR acceleration, the present day understanding is that shock waves and turbulence play an essential role in energizing both the electrons and ions present in the interstellar medium. We will perform linked experimental and numerical studies of the acceleration of electrons in strong shocks formed in magnetised plasmas. The shocks will be formed by supersonic plasma flows created by high intensity lasers and Mega-Ampere-level pulsed currents. The first set of experiments will investigate the initial acceleration of electrons, which should allow the formation of electron population with energies significantly exceeding their initial thermal energy. This is expected to occur due to plasma wave turbulence which is excited in the pre-shock plasma by the ions reflected from the shock front, but this mechanism has never been tested by experiment. We will characterise the development of the turbulence and measure the parameters of the accelerated electrons using state-of-the-art diagnostic techniques previously developed by us. In the second set of experiments, we will investigate the so-called diffusive shock acceleration mechanism, which is considered as the most plausible mechanism of cosmic ray acceleration. This will be achieved by injecting sufficiently energetic electrons into the shock, in such a way that these electrons will then sample both the pre- and post-shock regions, performing multiple passages through the shock front as required for this mechanism to operate efficiently. Use of a magnetic spectrometer will allow direct measurements of the energy of the accelerated electrons which will be compared with theoretical predictions. As part of this project we will also perform numerical simulations using state of the art hybrid-MHD and PIC codes and cross-compare the results with our experimental data. The computational and theoretical components of the project will allow us to forge a strong connection between experiment, astrophysical models and observations. The proposed research lies at the border between Plasma Physics and Astrophysics, and will advance the development of the novel research area of Laboratory Astrophysics, which seeks to enhance the understanding of the physics governing the behaviour of astrophysical objects directly via scaled laboratory experiments, combined with computer modelling. Creating the extreme plasma conditions required for scaled reconstruction of astrophysical environments in the laboratory, became possible only recently thanks to the advent of high energy lasers and fast rise-time high-current pulsed power facilities. The similarity between the lab and nature in terms of key dimensionless parameters (e.g. Mach number) is sufficiently close to make such experiments highly relevant. The timeliness of this proposal is also underlined by the growing interest in this field internationally with major efforts in USA (Rochester, Livermore - NIF) and Europe (Bordeaux - LaserMegajoule). The combined expertise of the authors of this proposal and the involvement of international collaborators from Astrophysics community will allow us to create and exploit an unprecedented capability for the Laboratory Astrophysics research and provide both breadth and depth to the programme.

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