In this thesis the effect of collective particle behaviour within a plasma was explored using kinetic plasma theory in conjunction with magnetohydrodynamics (MHD). Collisionless or quasi-collisionless space plasmas were used as test laboratories in an attempt to understand the evolution of space plasmas. In a collisionless plasma, forces and fields are mediated through collective behaviour such as instabilities and plasma waves, thus the plasma parameters evolve due to modification by collective effects. In this work we implemented analytical and numerical techniques to predict the effect of collective behaviour. These hypotheses were then tested against experimental data as a validation process. The region near the Earth’s bow shock where incoming solar wind interacts with plasma emanating from the bow shock is known as the foreshock. This region is an abundant source of complex particle distributions with associated collective phenomena. We report the first observation of correlation between elevated solar wind core plasma temperatures and temperature anisotropy in the terrestrial foreshock. Direct comparison of contemporaneous anisotropic temperatures in the upstream solar wind and the foreshock suggests that the net heating of plasma is mediated via a increase of the parallel temperature in the foreshock region where ultra low frequency (ULF) plasma waves have been observed. We consider the possibility that a mechanism based on Landau damping, where solar wind plasma temperature parallel to the background magnetic field is increased by interaction with oblique compressible fast magneto-acoustic ULF waves, influences temperature anisotropy. Next the impact of wave phenomena on the radio emission fine structure in flaring loops of the solar corona was investigated. In particular, the impact of MHD oscillations on zebra pattern (ZP) radio emission. Initially static analytical studies were carried in one and two dimensions to show it was possible do derive a ZP using MHD techniques. The dynamics of ZP formation in the presence of MHD oscillations were then analytically studied to show the presence of ‘wiggles’ in the ZP. These results were then repeated using numerical simulations using the Lare2D MHD code. The catalogue of results suggests that the detected ZP wiggles were caused by a standing sausage oscillation. We affirm this conclusion using the observation that both instant frequencies of individual stripes and their spectral separation oscillate with the same periods. Thus it is consistent with a sausage oscillation that perturb both the plasma density and magnetic field. These results are further underpinned by comparison to experimentally obtained ZP wiggles which exhibit similar periodicities. This new result could lead to a method for the direct measurement of coronal magnetic fields in flaring loops.

This thesis investigates the use of pulsed laser deposition (PLAD) for the preparation of metallic films and magnetic multilayers. Initial work focuses on the effects of the laser wavelength and the laser pulse temporal profile on the deposition rates of nickel and silver and the droplet numbers deposited on to films. The results show that the deposition of silver films is affected by the sputtering of material from the substrate by energetic ions in the plasma and that this leads to saturation of the deposition rate at high fluences. The saturation features are not as pronounced in nickel deposition rates. We see that droplet numbers are only weakly dependent upon the laser wavelength, with fewer being present at shorter wavelengths. The effect that the number of pulses has on droplet numbers is also investigated. In the case of the pulse profile study more droplets were observed on films deposited using the picosecond (ps) pulse profiles. As for the nanosecond (ns) pulse profile the saturation in the deposition rates was observed in silver but not in nickel. The results of the ps laser pulse profiles showed that the ns background was dominant in the ablation process. Two further investigations into reducing droplet numbers were performed. These showed that a uniform beam profile was not sufficient for eliminating droplets from the PLAD process and that the use of a tape target in conjunction with a ps pulse profile did not reduce droplet numbers either. The aims of the second section of this thesis were to assess the suitability of PLAD for depositing multilayers and obtain PylPt multilayers showing a sensitive giant magnetoresistance (GMR) effect at low applied magnetic field. Samples prepared by two PLAD systems and by RF sputtering were compared. An anisotropic magneto resistance effect was measured, however GMR was not. The multilayer structures were characterised using x-ray reflectivity and cross sectional transmission electron micrographs. The results showed greater uniformity in the layers deposited by sputtering than PLAD.

Since the invention of the bipolar transistor in 1947, lateral dimensions of semiconductor devices have reduced by a factor of 4 and in-depth dimensions by some two orders of magnitude. This size reduction is continually making the accurate measurement of the latest generation of semiconductor devices more difficult. Secondary ion mass spectrometry (SIMS) is a highly effective analytical technique, traditionally used to measure concentration depth profiles, due to its high sensitivity and good depth resolution. The development of the floating ion gun (FLIG) at Warwick, allows the routine use of sub-keV beam energies for rapid SIMS depth profiling. The aim of this research project was to find and investigate ultra-low energy SIMS depth profiling conditions, suitable for the accurate analysis of modern silicon semiconductor devices. This work has shown that ultra-low energy ion beams at normal incidence, not only produce the most accurate SIMS depth profiles, at 250 e V the entire depth scale is accurate to within 1.5 nm (2.5 nm at 500 eV), but also for boron with the highest depth resolution. Two significant errors introduced into the depth scale of calibrated boron depth profiles, the surface transient shift and a largely overlooked parameter - the terminal shift, were quantified. Utilising these two shifts a simple universal depth correction procedure has been described, applicable when profiling boron samples using 02+ at normal incidence. The development of surface topography has two detrimental effects, a loss in depth resolution and a variation in the sputter yield, both of which have been quantified. A wide range of analysis conditions were investigated, at 02+ beam energies up to 1 keY, the only angles where ripples do not develop within the top 200 nm of a profile are those using near-normal incidence (θp ≤ 30°) ion bombardment.

Detailed knowledge of the interaction of magnetic moments is key to developing the next generation of magnetic devices. Systems with induced moments provide an ideal regime in which to study this fundamental behaviour. Resonant x-ray scattering and polarised neutron reflectivity are complementarily used to map induced moment profiles in continuous FeZr/CoZr multilayer films and both continuous and patterned Pd/Fe/Pd trilayer films. Resonant scattering is additionally employed to measure the dimensionality of the magnetic lattice through observations of the magnetic ordering behaviour. The shape and extent of the induced profiles was resolved with unprecedented accuracy, and was found to conform to the theoretical expectation: all profiles decayed exponentially from the inducing material, with an extent in the nm regime. Adjacent magnetic lattices were found to interact only through the magnitude of their moments, acting through the magnetic susceptibility of the induced material. The dimensionality of adjacent magnetic lattices were therefore found to be independent. Additionally, a significant, and unexpected, observation was made of the thinnest Fe layers studied: the Fe moment was seen to vanish though a pronounced induced moment remained in the neighbouring Pd. The definitive cause of this unusual behaviour has yet to be discovered. In the patterned materials, the interaction between adjacent islands was found to contribute minimally to the overall behaviour in the geometry studied. The energy cost of rotating the moments within an individual island was the dominating contribution to the magnetic ordering behavior. These results provide new insight into the coupling mechanisms between adjacent moments, while revealing new complexities that provide the foundation for further study.

Arbitrary Lagrangian Eulerian methods are methods which seek to take advantage of the strengths of Eulerian and Lagrangian methods, whilst circumventing the weaknesses. This thesis discusses the development of such a code ,Odin, in two dimensions, for both Cartesian and cylindrical coordinates. Odin is capable of handling shocks through the addition of shock viscosity to the Euler equations. Furthermore the hydrodynamical scheme is expanded to include magnetohydrodynamics.

This thesis presents the branching fractions measurements of B0(s) -> J/ψK0Sh+h(')− (h(') = K,π) decays, corresponding to an integrated luminosity of 1.0 fb−1 of data recorded at a centre-of-mass energy of √s = 7TeV collected with the LHCb detector at CERN Large Hadron Collider (LHC) during 2011. The first observation of the B0s -> J/ψK0SK±π-+ decay is reported, with a significance greater than 10 standard deviations. The B0 -> J/ψK0SK+K− decay is also observed for the first time. The branching fraction of B0 -> J/ψK0Sπ+π− is determined, to significantly better precision than previous measurements, using B0 -> J/ψK0S as a normalisation channel. Branching fractions and upper limits of the other B0(s) -> J/ψK0Sh+h(')− modes are determined relative to that of the B0 -> J/ψK0Sπ+π− decay. The findings of this thesis have been submitted to JHEP as detailed in Ref. [1].

Swarming is a conspicuous behavioural trait observed throughout the animal kingdom. It is thought to improve collective awareness and over protection from predators. Self propelled particle (SPP) models are often compared with animal swarms and involve the hypothesis that information coordinating motion is exchanged between neighbours. We identify that minimal models for swarming must achieve a few key properties such as, polarisation, the global alignment of velocities, cohesion, high density that is robust to perturbation. These constraints still leave considerable freedom in the structure of these models. To tackle this degeneracy, and better distinguish between candidate models for polarisation, we first study swarms of SPPs circulating in channels where we permit information to pass through windows between neighbouring channels. Co-alignment between particles then couples the channels so that they tend to counter-rotate. We study channels arranged to mimic a geometrically frustrated antiferromagnet and show how the effects of this frustration allow us to better distinguish between SPP models. There is now experimental evidence that nearest-neighbour interactions in many swarms are metric free, but the models that control density rely on attractive and repulsive forces with associated length scales. We propose a solution that involves a metric-free motional bias on those individuals that are topologically identified to be on the surface of the swarm. We and a novel power-law scaling of the real-space density with the number of individuals N as well as a familiar order-to-disorder transition. We argue that local interactions alone are insufficient to explain the organisation of large flocks of birds and expand the strictly metric free model to mimic the information set and abilities of a starling in a murmuration. We postulate that large flocks self-organise to the maximum density at which a typical individual is still able to see out of the flock in many directions; such flocks are marginally opaque. The emergence of marginal opacity constrains how individuals interact with each other within swarms. It also provides a mechanism for global interactions: An individual can respond to the projection of the flock that it sees. We then present evidence for marginal opacity in starling murmurations observed around the UK.

Phosphate glasses for potential applications as bioactive materials have been studied using Solid state Nuclear Magnetic Resonance (NMR), owing to the fact that their bioactivity is strongly correlated to their atomic structure. A multinuclear NMR approach has been conducted on numerous series of phosphate bioactive glasses including 31P, 23Na, along with 27Al MAS NMR on a series of Al doped glasses, and the less widely studied 71Ga and 17O MAS NMR on multiple series of Ga doped glasses. In addition, the first implementation of the recently developed 31P refocused INADEQUATE Spin-Echo (REINE) experiment on a coherent series of glasses has been shown, providing greater insight into the distribution of J couplings throughout the phosphate network. Upon incorporation of Al into the phosphate network, 27Al MAS NMR has shown a subsequent change from initially octahedral to tetrahedral Al coordination. In addition, an increase in shielding and decrease in the quadrupolar parameter CQ of the Na ions from 23Na MAS NMR, along with a decrease in the 31P J coupling indicated from the REINE data, evidences the role of Al within the glass network cross linking phosphate chains, resulting in a strengthened more condensed network. In the Ga doped glass series the 71Ga MAS NMR data shows a similar trend for the Ga coordination as found in the Al series, with the 23Na MAS NMR also indicating comparable results. The 31P REINE results however, do not provide observable trends, thus indicating that the Ga is having a slight different in uence in the glass network to that of the Al cation. 17O 3QMAS results show the presence of both non bridging and bridging oxygens as expected in these systems. Mullite materials are of interest to material scientists owing to their favourable properties, making them ideal for `advanced ceramic' applications. However, the structure of mullite is complex owing to the disorder, arising from the vacancies present in the aluminosilicate network. A comprehensive multinuclear solid state MAS NMR investigation has been carried out on the structure of both undoped 3:2 mullite, and B doped 3:2 mullite materials. 27Al single pulse MAS NMR has enabled the identification of the octahedral and tetrahedral sites present, along with the 27Al 3QMAS experiment providing conclusive evidence of the Al tri-cluster sites in the structure. 100 % 29Si labelled samples have enabled the acquisition of quantitative and high resolution 29Si MAS NMR data, along with 29Si refocused INADEQUATE and f29Sig-27Al J-HMQC correlation experiments, providing detailed information on the connectivities in the aluminosilicate network. Both the 27Al and 29Si MAS NMR data have enabled determination of the nature of the tri-cluster site. 11B MAS NMR on B doped 3:2 mullite materials have shown B to occupy a BO3 coordination within the mullite structure according to a substitution with Si, cross linking the octahedral Al chains.

Tensor networks provide a powerful and elegant approach to quantum manybody simulation. The simplest example is the density matrix renormalisation group (DMRG), which is based on the variational update of a matrix product state (MPS). It has proved to be the most accurate approach for the numerical study of strongly correlated one dimensional systems. We use DMRG to study the one dimensional disordered Bose-Hubbard model at fillings N=L = 1=2, 1 and 2 and show that the whole phase diagram for each can be successfully obtained by analysing entanglement properties alone. We �nd that the average entanglement is insufficient to accurately locate all of the phases, however using the standard error on the mean we are able to construct a phase diagram that is consistent with previous studies. It has recently been shown that there is a connection between the geometry of tensor networks and the entanglement and correlation properties that it can encode, which is a generalisation of the so called area law for entanglement entropy. This suggests that whilst gapped quantum systems can be accurately modeled using an MPS, a tensor network with a holographic geometry is natural to capture the logarithmic entanglement scaling and power law decaying correlation functions of critical systems. We create an algorithm for the disordered Heisenberg Hamiltonian that self assembles a tensor network based on the disorder in the couplings. The geometry created is that of a disordered tree tensor network (TTN) that when averaged has the holographic properties characteristic of critical systems. We continue the analysis of holographic tensor network geometry by considering the average length of leaf-to-leaf paths in various tree graphs, which is related to two-point correlation functions in tensor networks. For regular, complete trees we analytically calculate the average path length and all statistical moments, and generalise it for any splitting number. We then turn to the Catalan trees, which is the set of unique binary trees with n vertices, as it has a similar geometry to the disordered TTNs. We calculate the average depth of a leaf and show that it is equal to the average path length. We compare these analytic results with the structures found in the TTN and randomly constructed trees to show that the renormalisation involved in the TTN algorithm is crucial in the selection of the tree structure.

Roughly two-thirds of all stars are locked in binary or higher-multiple systems. Given that over 97% of all stars also end their lives as white dwarfs, it is not surprising that more and more white dwarfs are being found as part of binary systems. A general introduction to white dwarfs and binary stars is presented in Chapter 1 and the techniques used throughout this thesis are presented in Chapter 2. Then, Chapters 3 and 4 present detailed studies of two close double white dwarf binaries. The first, CSS 41177, is also an eclipsing binary, which allows for detailed measurements of the white dwarf masses and radii. With the help of statistical analyses of far-ultraviolet spectroscopy from the Hubble Space Telescope, I also determine the effective temperatures and surface gravities of both stars. For the second binary, SDSS J1257+5428, previous publications were inconclusive, and therefore prompted the far-ultraviolet HST observations featured in this thesis. Using these data, I present a detailed analysis of the system and the still paradoxical results which indicate that the more massive of the two white dwarfs is younger rather than older than its lower-mass white dwarf companion. In Chapter 5 I detail the observations and aims of my eclipse timing programme, set up to measure apparent and/or real variations in the orbital periods of close white dwarf binaries. With more than 600 high-speed eclipse light curves, spread over more than 70 targets, I try to find general trends and hints of the underlying cause of such variations. Chapter 6 then presents a detailed study of the eclipsing semi-detached white dwarf + M-dwarf binary HUAqr, which is part of the timing programme. In fact, it is one of the most controversial targets in this programme, since none of the theoretical explanations fit the large-scale eclipse timing variations observed in this binary. Finally, I end with a concluding summary in Chapter 7.