The Rutherford Appleton Laboratory is one of the national scientific research laboratories in the UK operated by the Science and Technology Facilities Council . It is located on the Harwell Science and Innovation Campus at Chilton near Didcot in Oxfordshire, United Kingdom. It has a staff of approximately 1,200 people who support the work of over 10,000 scientists and engineers, chiefly from the university research community. The laboratory's programme is designed to deliver trained manpower and economic growth for the UK as the result of achievements in science. Wikipedia.
News Article | May 12, 2017
Space radiation has been reproduced in a lab on Earth. Scientists have used a laser-plasma accelerator to replicate the high-energy particle radiation that surrounds our planet. The research could help study the effects of space exploration on humans and lead to more resilient satellite and rocket equipment. The radiation in space is a major obstacle for our ambitions to explore the solar system. Highly energetic ionizing particles from the Sun and deep space are extremely dangerous for human health because they can pass right through the skin and deposit energy, irreversibly damaging cells and DNA. On top of that, the radiation can also wreak havoc on satellites and equipment. While the most obvious way to study these effects is to take experiments into space, this is very expensive and impractical. Yet doing the reverse – producing space-like radiation on Earth – is surprisingly difficult. Scientists have tried using conventional cyclotrons and linear particle accelerators. However, these can only produce monoenergetic particles that do not accurately represent the broad range of particle energies found in space radiation. Now, researchers led by Bernhard Hidding from the University of Strathclyde in the UK have found a solution. The team used laser-plasma accelerators at the University of Dusseldorf and the Rutherford Appleton Laboratory to produce broadband electrons and protons typical of those found in the van-Allen belts – zones of particle radiation caused by Earth's protective magnetic fields. The accelerator works by firing a high-energy, high-intensity laser at a tiny spot just a few μm2 on a thin-metal-foil target. "The sheer intensity of the laser pulse means that the electric fields involved are orders of magnitude larger than the inneratomic Coulomb forces," explains Hidding, "The metal-foil target is therefore instantly converted into a plasma." The plasma particles – electrons and protons – are accelerated by the intense electromagnetic fields of the laser and the collective fields of the other plasma particles. The extent at which this happens depends on the particle's initial position, resulting in the huge range of energies. The team studied its plasma particles using electron-sensitive image plates, radiochromic films for protons and scintillating phosphor screens. Then, to prove the lab-made radiation was comparable to space radiation, the team used simulations from NASA. "The NASA codes are based on models as well as a few measurements, so they represent the best knowledge we have," says Hidding. The next task was to prove that the system could be used to test the effects of space radiation by subjecting optocouplers to the particle radiation. Optocouplers are common devices that transfer electric signals between isolated circuits. As they are characterized by their current transfer ratio, Hidding and team were able to monitor the radiation-induced degradation by measuring this performance. The proof-of-concept experiment, described in Scientific Reports, could represent a major breakthrough towards understanding the effects of space radiation without the need to leave Earth. The next step will be to develop a testing standard that can be used to test electronics and biological samples – "After all, radiation in space is one of the key showstoppers for human spaceflight," Hidding remarks. Strathclyde's newly installed laser will also play a key role in future research – "[It is] the highest-average-power laser system in the world today," says Hiddings. Housed in three radiation-shielded bunkers at the Scottish Centre for the Application of Plasma-based Accelerators (SCAPA), the system will power up to seven beamlines. "The vision is to develop a dedicated beamline for space-radiation reproduction and testing, and to put this to use for the growing space industry in the UK and beyond."
Maire E.,CNRS Laboratory for Materials: Engineering and Science |
Withers P.J.,Manchester X ray Imaging Facility |
Withers P.J.,Rutherford Appleton Laboratory
International Materials Reviews | Year: 2014
X-ray computer tomography (CT) is fast becoming an accepted tool within the materials science community for the acquisition of 3D images. Here the authors review the current state of the art as CT transforms from a qualitative diagnostic tool to a quantitative one. Our review considers first the image acquisition process, including the use of iterative reconstruction strategies suited to specific segmentation tasks and emerging methods that provide more insight (e.g. fast and high resolution imaging, crystallite (grain) imaging) than conventional attenuation based tomography. Methods and shortcomings of CT are examined for the quantification of 3D volumetric data to extract key topological parameters such as phase fractions, phase contiguity, and damage levels as well as density variations. As a non-destructive technique, CT is an ideal means of following structural development over time via time lapse sequences of 3D images (sometimes called 3D movies or 4D imaging). This includes information needed to optimise manufacturing processes, for example sintering or solidification, or to highlight the proclivity of specific degradation processes under service conditions, such as intergranular corrosion or fatigue crack growth. Besides the repeated application of static 3D image quantification to track such changes, digital volume correlation (DVC) and particle tracking (PT) methods are enabling the mapping of deformation in 3D over time. Finally the use of CT images is considered as the starting point for numerical modelling based on realistic microstructures, for example to predict flow through porous materials, the crystalline deformation of polycrystalline aggregates or the mechanical properties of composite materials. © 2014 Institute of Materials, Minerals and Mining and ASM International.
Guidi T.,Rutherford Appleton Laboratory
Nature Physics | Year: 2017
The twin discoveries of the quantum Hall effect, in the 1980s, and of topological band insulators, in the 2000s, were landmarks in physics that enriched our view of the electronic properties of solids. In a nutshell, these discoveries have taught us that quantum mechanical wavefunctions in crystalline solids may carry nontrivial topological invariants which have ramifications for the observable physics. One of the side effects of the recent topological insulator revolution has been that such physics is much more widespread than was appreciated ten years ago. For example, while topological insulators were originally studied in the context of electron wavefunctions, recent work has initiated a hunt for topological insulators in bosonic systems: in photonic crystals, in the vibrational modes of crystals, and in the excitations of ordered magnets. Using inelastic neutron scattering along with theoretical calculations, we demonstrate that, in a weak magnetic field, the dimerized quantum magnet SrCu2(BO3)2 is a bosonic topological insulator with topologically protected chiral edge modes of triplon excitations. © 2017 Nature Publishing Group
Keen D.A.,Rutherford Appleton Laboratory |
Goodwin A.L.,University of Oxford
Nature | Year: 2015
Classical crystallography can determine structures as complicated as multi-component ribosomal assemblies with atomic resolution, but is inadequate for disordered systems - even those as simple as water ice - that occupy the complex middle ground between liquid-like randomness and crystalline periodic order. Correlated disorder nevertheless has clear crystallographic signatures that map to the type of disorder, irrespective of the underlying physical or chemical interactions and material involved. This mapping hints at a common language for disordered states that will help us to understand, control and exploit the disorder responsible for many interesting physical properties. © 2015 Macmillan Publishers Limited. All rights reserved.
Parker S.F.,Rutherford Appleton Laboratory
Chemical Communications | Year: 2011
Using the unique ability of inelastic neutron scattering spectroscopy to quantify surface hydroxyls, it is shown that two hydroxyls are essential for the low temperature oxidation of CO over a model palladium catalyst. © 2011 The Royal Society of Chemistry.
Soper A.K.,Rutherford Appleton Laboratory
Journal of Physics Condensed Matter | Year: 2012
Recently, water absorbed in the porous silica material MCM-41-S15 has been used to demonstrate an apparent fragile to strong dynamical crossover on cooling below 220K, and also to claim that the density of confined water reaches a minimum at a temperature around 200K. Both of these behaviours are purported to arise from the crossing of a Widom line above a conjectured liquidliquid critical point in bulk water. Here it is shown that traditional estimates of the pore diameter in this porous silica material (of order 15) are too small to allow the amount of water that is observed to be absorbed by these materials (around 0.5g H 2O/g substrate) to be absorbed only inside the pore. Either the additional water is absorbed on the surface of the silica particles and outside the pores, or else the pores are larger than the traditional estimates. In addition the low Q Bragg intensities from a sample of MCM-41-S15 porous silica under different dry and wet conditions and with different hydrogen isotopes are simulated using a simple model of the water and silica density profile across the pore. It is found the best agreement of these intensities with experimental data is shown by assuming the much larger pore diameter of 25(radius 12.5). Qualitative agreement is found between these simulated density profiles and those found in recent empirical potential structure refinement simulations of the same data, even though the latter data did not specifically include the Bragg peaks in the structure refinement. It is shown that the change in the (100) peak intensity on cooling from 300 to 210K, which previously has been ascribed to a change in density of the confined water on cooling, can equally be ascribed to a change in density profile at constant average density. It is further pointed out that, independent of whether the pore diameter really is as large as 25or whether a significant amount of water is absorbed outside the pore, the earlier reports of a dynamic crossover in supercooled confined water could in fact be a crystallization transition in the larger pore or surface water. © 2012 IOP Publishing Ltd.
Parker S.F.,Rutherford Appleton Laboratory
Coordination Chemistry Reviews | Year: 2010
Of the challenges that are still to be met to enable the widespread use of H2 as a fuel for automotive applications, a safe, reliable and cheap method for its storage and transportation is paramount. This need has prompted a massive effort in the synthesis and characterisation of novel hydrides and a better understanding of existing materials. In this review the vibrational spectroscopy and the bonding of a wide range of ternary metal hydride complexes are discussed. The spectroscopic techniques used include transmission and photoacoustic infrared spectroscopy, Raman spectroscopy with excitation wavelengths ranging from 1064 to 515 nm, inelastic neutron scattering spectroscopy and nuclear resonant inelastic X-ray scattering spectroscopy. The systems studied are: the octahedral transition metal hydrides, other geometry's of transition metal hydrides, alkali metal, alkaline earth and aluminium compounds with the borohydride ion, the alkali metal and alkaline earth alanates and the alkali metal gallates. In all cases, while the central atom is the most important determinant of the properties, it has become increasingly clear that the counter-ion is much more than just a spectator; it often plays a key role in determining the stability of the material. As such, varying the counter-ion provides an important mechanism for optimising the desired properties and these are reflected in the spectra. In addition to its use in characterising materials, vibrational spectroscopy is used to investigate reactions and processes. The advantages of vibrational spectroscopy lie in its flexibility: it is not restricted to crystalline systems, amorphous or nanocrystalline materials are readily observable, it is amenable to in situ studies, it is democratic; infrared and Raman spectroscopy are not element specific and uniquely among probes they are able to follow a reaction across a change of state. Vibrational spectroscopy and ab initio calculations are a synergistic pairing. Comparison of computed and experimental spectra provides a stringent test of the calculation, while the calculation provides unambiguous assignments of the spectra. Generation of the inelastic neutron scattering spectrum provides the most reliable test since only the amplitude of motion of the atoms in each mode is required. © 2009 Elsevier B.V. All rights reserved.
Lebedev A.A.,Rutherford Appleton Laboratory |
Isupov M.N.,University of Exeter
Acta Crystallographica Section D: Biological Crystallography | Year: 2014
The presence of pseudo-symmetry in a macromolecular crystal and its interplay with twinning may lead to an incorrect space-group (SG) assignment. Moreover, if the pseudo-symmetry is very close to an exact crystallographic symmetry, the structure can be solved and partially refined in the wrong SG. Typically, in such incorrectly determined structures all or some of the pseudo-symmetry operations are, in effect, taken for crystallographic symmetry operations and vice versa. A mistake only becomes apparent when the R free ceases to decrease below 0.39 and further model rebuilding and refinement cannot improve the refinement statistics. If pseudo-symmetry includes pseudo-translation, the uncertainty in SG assignment may be associated with an incorrect choice of origin, as demonstrated by the series of examples provided here. The program Zanuda presented in this article was developed for the automation of SG validation. Zanuda runs a series of refinements in SGs compatible with the observed unit-cell parameters and chooses the model with the highest symmetry SG from a subset of models that have the best refinement statistics. © 2014 International Union of Crystallography.
David W.I.F.,Rutherford Appleton Laboratory
Faraday Discussions | Year: 2011
This paper gives an overview of the current status and future potential of hydrogen storage from a chemistry perspective and is based on the concluding presentation of the Faraday Discussion 151 - Hydrogen Storage Materials. The safe, effective and economical storage of hydrogen is one of the main scientific and technological challenges in the move towards a low-carbon economy. One key sector is transportation where future vehicles will most likely be developed around a balance of battery-electric and hydrogen fuel-cell electric technologies. Although there has been a very significant research effort in solid-state hydrogen storage, high-pressure gas storage combined with conventional metal hydrides is still seen as the current intermediate-term candidate for car manufacturers. Significant issues have arisen in the search for improved solid-state hydrogen storage materials; for example, facile reversibility has been a major challenge for many recently studied complex hydrides while physisorption in porous structures is still restricted to cryogenic temperatures. However, many systems fulfil the majority of necessary criteria for improved hydrogen storage - indeed, the discovery of reversibility in multicomponent hydride systems along with recent chemistry breakthroughs in off-board and solvent-assisted regeneration suggest that the goal of both improved on-board reversible and off-board regenerated hydrogen storage systems can be achieved. © The Royal Society of Chemistry 2011.
Krissinel E.,Rutherford Appleton Laboratory
Acta Crystallographica Section D: Biological Crystallography | Year: 2011
This paper presents a discussion of existing methods for the analysis of macromolecular interactions and complexes in crystal packing. Typical situations and conditions where wrong answers may be obtained in the course of ordinary procedures are presented and discussed. The more general question of what the relationship is between natural (in-solvent) and crystallized assemblies is discussed and researched. A computational analysis suggests that weak interactions with K d ≥ 100 μM have a considerable chance of being lost during the course of crystallization. In such instances, crystal packing misrepresents macromolecular complexes and interactions. For as many as 20% of protein dimers in the PDB the likelihood of misrepresentation is estimated to be higher than 50%. Given that weak macromolecular interactions play an important role in many biochemical processes, these results suggest that a complementary noncrystallographic study should be always conducted when inferring structural aspects of weakly bound complexes.