Fluid Theory and Simulation for Laser-Plasma Interactions

Our research embraces the areas of nonlinear physics and soliton theory, as applied in plasma physics and laser-plasma interactions. We shall make extensive use of the paradigm of a soliton, that is a structure (e.g., bell-shaped) which is localised in space and possesses a stationary profile which remains unchanged in time. Typical examples of soliton-relevant contexts include tsunamis and rogue/freak waves in the ocean, optical pulses in fiber optics, signal transmission across membranes, and others. Solitons owe their remarkable properties to a delicate balance between dispersion and nonlinearity, also undergoing generic physical mechanisms, such as perturbations, dissipation, noise (due to turbulence in the background), to mention but a few. In an idealised picture, solitons survive through mutual collisions, which makes them significant entities to support information and signal transcmission in various media (nonlinear optics, condensed matter physics). In plasma physics, solitons occur in the modelling of propagating localised electromagnetic/electrostatic modes, which occur in abundance in experimental or Space observations. Notwithstanding the different scales of parameters involved, localised structures are ubiquitous in plasmas at all levels, including laboratory plasmas (e.g. experiments on low-temperature discharge plasmas and on laser-matter interactions at the host Centre, CPP/QUB), Space plasmas (e.g. in the magnetosphere, the physics of the bow shock, or the Earth's aurora), astrophysics (pulsar radio emission is associated to solitons) and dusty plasmas in the interstellar space. We therefore expect our findings to be of relevance in various areas of plasma physics and certainly of interest to researchers in the UK and overseas. We aim at studying the dynamics of electromagnetic solitons in laser plasmas. Laser-plasma interaction (LPI) is perhaps the fastest evolving area in modern plasma science. Apart from its challenging relevance in inertial confinement fusion (ICF) schemes, the area of LPI bears a vast field of applications in industry and technology (e.g. laser design for microelectronics application, perspective for improved laser based appliances). A great amount of fundamental (theoretical) and experimental research is now carried out in the UK and worldwide, boosted by tremendous possibilities of new generation lasers producing ultrashort pulses at ultrahigh intensities. The host Centre (CPP/QUB) boasts some of the leading experimental groups in the UK in LPI.The aim and scope of the proposed research consist of a comprehensive investigation of the dynamics of intense electromagnetic pulses in plasmas, employing analytical and numerical techniques from nonlinear fluid plasma theory. Our aim is to investigate previously unexplored aspects of EM solitary wave propagation, in particular focusing on two-dimensional (2D) geometry effects on EM soliton propagation. A number of relevant areas will be investigated. The derivation of two-dimensional (2D) soliton evolution equations will be undertaken from the fluid-Maxwell model. The soliton equilibrium equations will be solved to obtain the field profiles associated with the soliton. A two dimensional fluid code will then be developed. The numerical soliton solution will be used as initial condition for the time evolution studies. The propagation of 2D solitons in uniform as well as non-uniform plasma will be investigated using a fluid code, by considering different types of density inhomogeneity. If the solitons are found stable in homogeneous plasma, mutual collisions among two solitons will be studied in a realistic parameter regime. This should provide the possibility for a direct comparison of these solitons with the known topological solitons. Furthermore, we envisage to focus in particular on an extensive multiscale analysis of laser pulse dynamics to extend and improve earlier theorie

The project bears significant potential for impact, both at national (UK) and international level. Academic, societal and economic impact and targeted beneficiaries are outlined below. Relevance to energy production schemes - the fusion vision. Laser-plasma interaction is of relevance to Inertial Confinement Fusion (ICF), a well-known scenario for controlled thermonuclear fusion, which should one day enable safe and sustainable energy production for the generations to come. It is known that ultra-high-energy laser-produced EM pulses may effectively carry the energy required for fusion to occur all the way to the core (ignition target). The need for elucidation of the pulse propagation mechanism(s) is thus more than apparent, so our research should affect the theoretical foundation of ICF significantly. We anticipate our research to draw attention among other researchers,and eventually to contribute to a realistic path towards fusion. The output of our research will be presented in specialised scientific meetings in the field, and may also be taught as lecture material (details below). A direct academic impact is expected, both in the UK and internationally, to be marked not only at a specialised level, but also at a wider audience scale (societal impact). Relevance to experimental research. We draw inspiration from experiments on the interaction of ultra-short ultra-intense electromagnetic pulses with plasmas, in the UK and abroad. Localised structure formation is abundantly observed in those experiments, along with numerous instabilities which affect the stability profile of waves and the intrinsic properties of the plasma. We expect a direct and immediate impact of our research findings in those areas. Impact at this level will be fostered by direct interactions with interested teams, in the host Centre (Belfast) and elsewhere. Methods for communications and engagement. We plan to offer the widest dissemination possible to our research, via a) announcements at conferences, b) vivid participation to thematic academic forae and c) publication in high-impact international journals ensuring wide visibility. Links to other disciplines will be investigated. Societal and academic impact via training, human potential, curriculum development Our research output may form part of lecture material, to train young people. Training curriculae (existing and under construction) and benefit mechanisms include: a) incorporating research output in taught material in web-based MSc programmes in the UK (MSc in Plasma Physics) and internationally (EU Erasmus IP on HiPER related physics; EU Summer School on Plasma Physics); b) involving project-related staff into extensive training and supervision activities by postgraduate students; c) exchange of know-how with interested beneficiaries in both academic and private sectors. A number of students will carry out their master's research projects (leading to dissertations and original article publications) with us, bringing new momentum to the project and also offering themselves new perspectives, by acquiring new knowledge and expertise. Novel analytical and computational techniques will be developed in the context of the project research. These will contribute to a transfer of knowledge to young students and researchers. As a clear pathway to impact, this acquired know-how can be used e.g. in a career in the energy sector (societal impact, UK and EU-wide). Industrial, economic and societal impact via applied research Technological applications make increasing use of laser devices. Plasmas have been proposed as an effective medium to be used as a waveguide ( plasma lens ). The elucidation of the mechanism of interaction between plasma and a laser beam is of outmost importance in the economy of the years to come. We will invest time and effort in assessing the potential of our findings, eventually probing interest among companies in the technological sector