A5043472004- Fusion materials and technologies
- Nuclear Materials and Properties
- Ion-surface interactions and analysis
- Microstructure and mechanical properties
- Advanced Materials Characterization Techniques
- High-pressure geophysics and materials
- Advanced materials and composites
- Plasmonic and Surface Plasmon Research
- Near-Field Optical Microscopy
- Nuclear materials and radiation effects
- Gold and Silver Nanoparticles Synthesis and Applications
- Advanced Chemical Physics Studies
- Photonic Crystals and Applications
- Organic Electronics and Photovoltaics
- Spectroscopy and Quantum Chemical Studies
- Machine Learning in Materials Science
- Optical Coatings and Gratings
- Photonic and Optical Devices
- Nuclear Physics and Applications
- nanoparticles nucleation surface interactions
- Microfluidic and Bio-sensing Technologies
- Orbital Angular Momentum in Optics
- Thermal properties of materials
- Hydrogen embrittlement and corrosion behaviors in metals
- Nuclear reactor physics and engineering
United Kingdom Atomic Energy Authority
2017-2025
Culham Science Centre
2014-2024
Culham Centre for Fusion Energy
2014-2024
University of Oxford
2004-2019
Université Paris-Saclay
2019
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2019
CEA Paris-Saclay
2019
Helsinki Institute of Physics
2019
University of Helsinki
2019
Université de Lille
2019
Under the anticipated operating conditions for demonstration magnetic fusion reactors beyond ITER, structural and plasma-facing materials will be exposed to unprecedented of irradiation, heat flux, temperature. While such extreme environments remain inaccessible experimentally, computational modeling simulation can provide qualitative quantitative insights into response complement available experimental measurements with carefully validated predictions. For components as first wall divertor,...
Using in-situ transmission electron microscopy, we have directly observed nano-scale defects formed in ultra-high purity tungsten by low-dose high energy self-ion irradiation at 30K. At cryogenic temperature lattice reduced mobility, so these microscope observations offer a window on the initial, primary damage caused individual collision cascade events. Electron images provide direct evidence for power-law size distribution of high-energy cascades, with an upper limit independent incident...
Using _in situ_ transmission electron microscopy (TEM), we have observed nanometre scale dislocation loops formed when an ultra-high-purity tungsten foil is irradiated with a very low fluence of self-ions. Analysis the TEM images has revealed largest to be predominantly prismatic 1/2<111> type and vacancy character. The formation such surprising since isolated are expected highly mobile, should escape from foil. In this work show that size number density can explained by fact _not_ - in...
Abstract Knowledge of mechanical and physical property evolution due to irradiation damage is essential for the development future fission fusion reactors. Ion-irradiation provides an excellent proxy studying damage, allowing high doses without sample activation. Limited ion-penetration-depth means that only few-micron-thick damaged layers are produced. Substantial effort has been devoted probing properties these thin implanted layers. Yet, whilst key reactor design, their thermal transport...
At temperatures below the onset of vacancy migration, metals exposed to energetic ions develop dynamically fluctuating steady-state microstructures. Statistical properties these microstructures in asymptotic high exposure limit are not universal and vary depending on energy mass incident ions. We a model for microstructure an ion-irradiated metal under athermal conditions, where internal stress fluctuations dominate kinetics structural evolution. The balance between defect production...
Atomistic simulations are a primary means of understanding the damage done to metallic materials by high energy particulate radiation. In many situations electrons in target material known exert strong influence on rate and type damage. The dynamic exchange between ions can act damp ionic motion, inhibit production defects or quench damage, depending situation. Finding ways incorporate these electronic effects into atomistic radiation is topic current major interest, driven science...
The solid immersion lens (SIL) is a well-developed near-field optical device for imaging and data storage. Recent experiments have demonstrated high-quality beyond the diffraction limit by nanoscale lenses in an SIL-type implementation [Nature 460, 498 (2009)]; we call these nSIL. A question arises as to what resolution obtainable with From full three-dimensional, finite-difference time-domain calculations, demonstrate that FWHM of focal spot objective-lens-nSIL system can be reduced greater...
We use time-dependent density functional theory to study self-irradiated Si. calculate the electronic stopping power of Si in by evaluating energy transferred electrons per unit path length an ion kinetic from 1 eV 100 keV moving through host. Electronic is found be significant below threshold velocity normally identified with transitions across band gap. A structured crossover at low exists place a hard threshold. An analysis time dependence transition rates using coupled linear rate...
Predicting strains, stresses and swelling in nuclear power plant components exposed to irradiation directly from the observed or computed defect dislocation microstructure is a fundamental problem of fusion design that has so far eluded practical solution. We develop model, free parameters not accessible direct evaluation observation, able provide estimates for irradiation-induced strains on macroscopic scale, using information about distribution radiation defects produced by high-energy...
We present an empirical interatomic potential for tungsten, particularly well suited simulations of vacancy-type defects. compare energies and structures vacancy clusters generated with the extensive new database values computed using density functional theory, show that predicts low-energy defect formation high accuracy. A significant difference to other popular embedded-atom potentials tungsten is correct prediction surface energies. Interstitial properties short-range pairwise behaviour...
The sizes of defect clusters, produced in materials by energetic ion or neutron impacts, are critically important input for models describing microstructural evolution irradiated materials. We propose a model the distribution vacancy and self-interstitial clusters formed high-energy impacts tungsten, provide new data from situ irradiation experiments to validate model. predicts statistics sub-cascade splitting resulting primary defects extending over entire range cluster sizes, is able...
Combining spatially resolved X-ray Laue diffraction with atomic-scale simulations, we observe how ion-irradiated tungsten undergoes a series of non-linear structural transformations increasing irradiation exposure. Nanoscale defect-induced deformations accumulating above 0.02 displacements per atom (dpa) lead to highly fluctuating strains at ~0.1 dpa, collapsing into driven quasi-steady state ~1 dpa. The asymptotic is characterized by finely dispersed vacancy defects coexisting an extended...
Plasmonic effects associated with localized surface plasmon (LSP) resonances such as strong light trapping, large scattering cross-section, and giant electric field enhancement have received much attention for the more efficient harvesting of solar energy. Notably, even thickness active layer is significantly reduced, optical absorption capability a cell could be maintained incorporation plasmonic effects. This especially important development bulk heterojunction (BHJ) organic cells (OSCs),...
In a fusion tokamak, the plasma of hydrogen isotopes is in contact with tungsten at surface divertor. bulk material, concentration profile tends towards dynamic equilibrium between flux incident ions and their trapping release from defects, either native or produced by ion neutron irradiation. The dynamics exchange material controlled pressure, temperature, also energy barriers characterizing diffusion de-trapping defects. this work, we extend treatment interaction vacancy-type investigate...
Abstract The occurrence of high stress concentrations in reactor components is a still intractable phenomenon encountered fusion design. Here, we observe and quantitatively model non-linear high-dose radiation mediated microstructure evolution effect that facilitates fast relaxation the most challenging low-temperature limit. In situ observations tensioned tungsten wire exposed to high-energy ion beam show internal up 2 GPa relaxes within minutes, with extent time-scale accurately predicted...
High-shear methods have long been used in experiments to refine grain structures metals, yet the underlying mechanisms remain elusive. We demonstrate a refinement process using molecular dynamic simulations of iron wherein nanocrystalline are generated from initially perfect lattices under high-shear strain. The simulation cells undergo highly disordered state, followed by an atomic reordering and coarsening, resulting nanograins. explore dependence on parameters such as temperature, heat...
We performed ab initio density functional theory simulations of $\frac{1}{2}\ensuremath{\langle}111\ensuremath{\rangle}$ interstitial dislocation loops, closed and open vacancy $\ensuremath{\langle}100\ensuremath{\rangle}$ voids in tungsten, using simulation cells involving from 2000 to 2700 atoms. The size the loops transcends microscopic scale reaches mesoscopic where asymptotic elasticity treatment applies. Comparing formation energies voids, we conclude that a void remains most...
Hydrogen isotopes are retained in materials for fusion power applications, changing both hydrogen embrittlement and tritium inventory as the microstructure undergoes irradiation damage. But modelling of highly damaged - exposed to over 0.1 displacements per atom (dpa) where asymptotic saturation is observed, example tungsten facing plasma a tokamak reactor, difficult because cannot be treated weakly interacting isolated defect traps. In this paper we develop computational techniques find...
We investigate the transfer of energy from a harmonically oscillating atom in metal to electronic subsystem, using direct simulation method based on time-dependent tight-binding (TDTB). present our results terms viscous damping coefficient β enable comparison with previous MD and Langevin dynamics simulations, over an ionic range relevant for radiation damage. Analysis perturbation theory shows that rate electrons is independent frequency driven at high temperatures, but low temperature may...
Self-ion irradiation of pure tungsten with 2 MeV W ions provides a way simulating microstructures generated by neutron in components fusion reactor. Transmission electron microscopy (TEM) has been used to characterize defects formed samples ion irradiation. It was found that irradiated 0.85 dpa at relatively low temperatures develops characteristic microstructure dominated dislocation loops and black dots. The density size distribution these were estimated. Some the exposed self-ion then...
We describe the parameterization of a tungsten-hydrogen empirical potential designed for use with large-scale molecular dynamics simulations highly irradiated tungsten containing hydrogen isotope atoms, and report test results. Particular attention has been paid to getting good elastic properties, including relaxation volumes small defect clusters, interaction energy between isotopes typical irradiation-induced defects in tungsten. conclude that ordering changes ratio H atoms point defects,...