A5018269399- Magnetic confinement fusion research
- Dust and Plasma Wave Phenomena
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Plasma Diagnostics and Applications
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Solar and Space Plasma Dynamics
- Nuclear reactor physics and engineering
- High-pressure geophysics and materials
- Earthquake Detection and Analysis
- Laser-induced spectroscopy and plasma
- Nuclear Materials and Properties
- High-Energy Particle Collisions Research
Royal Military Academy
2020
Imperial College London
2008-2018
The 2014–2016 JET results are reviewed in the light of their significance for optimising ITER research plan active and non-active operation. More than 60 h plasma operation with first wall materials successfully took place since its installation 2011. New multi-machine scaling type I-ELM divertor energy flux density to is supported by principle modelling. relevant disruption experiments modelling reported a set three mitigation valves mimicking setup. Insights L–H power threshold Deuterium...
The dynamical behavior of dust produced in tokamaks is an important issue for fusion. In this work, the current status (DTOKS) [J. D. Martin et al., Europhys Lett. 83, 65001 (2008)] transport code will be presented. A detailed description various elements its underlying physical model given together with representative simulation results mega amp spherical tokamak (MAST) [A. Sykes Nucl. Fusion 41, 1423 (2001)]. Furthermore, a brief components (DUSTT) [R. Smirnov Plasma Phys. Controlled 49,...
In this contribution, we report on experiments performed in MAST to investigate dust creation, transport and influence plasma performance. The exceptional diagnostic access of allows stereoscopic imaging particles' motion both the divertor main chamber, utilizing fast infrared cameras. This technique 3D trajectory particles be reconstructed. Infrared creation during disruptions revealed an isotropic release from surface with very high velocities (up 350 m s −1 ). Stereoscopic has been used...
Recent studies dedicated to the characterisation of in-vessel dust in JET with new ITER-like wall (ILW) show that levels are orders magnitude lower compared latter stages carbon-wall (CW) period and decreasing operational time. Less than 1 g was recovered a recent inspection, more 200 material at end JET-CW life. inspection ILW shows low rates re-deposition only small areas damage type likely create particulate matter. Quantifiers from laser scattering techniques also indicate an order...
The DTOKS code, which models dust transport through tokamak plasmas, is described. floating potential and charge of a grain in plasma the fluxes energy to from it are calculated. From this model, temperature can be estimated. A background supplied by standard edge modelling code (B2SOLPS5.0), MAST (the MegaAmp Spherical Tokamak) ITER plasmas presented. We conclude that micron-radius tungsten reach separatrix ITER.
Dust immersed in plasma quickly charges to a potential where the ion and electron currents its surface balance; this is floating potential. In order accurately determine dust behavior, must be known. The charging of grains that are small with respect Debye length (${\ensuremath{\lambda}}_{D}$) may adequately approximated using orbital-motion-limited (OML) approach. A modified version OML presented for large both stationary flowing plasmas. This compared simulation found good agreement....
The classical source-collector sheath system describes a plasma that forms between Maxwellian source and an absorbing wall. is assumed to be collisionless without ionization. Two distinct areas are being formed: the collector sheath, ion-rich region in contact with boundary, which electron-rich area near source. In this work, we study modified version of system, where wall no longer but emits electrons. As result, have two different types one potential well formed well. We examine effect...
Dust produced in tokamaks is an important issue for fusion. particles can introduce health and safety issues when the same time have impact on reactor performance. Apart from associated problems there are also potential benefits that make better understanding of their behavior important. In this work dust transport code TOKamakS will be used to explore effect variations plasma background physical model, describing plasma-dust interaction, predicted trajectories.
Dust immersed in plasma quickly charges to a potential where the ion and electron currents it balance; this is floating potential. In order determine dust behaviour must be known. The most used theory for determining orbital motion limited (OML). OML depends on temperature ratio (β) species (A). reality also strongly size of grain (ρ = a/λD, radius λD Debye length). Using particle-in-cell code, simulated collisionless plasma, investigated expressions provided allowing fast accurate...
In this work modifications of the orbital motion limited approach are used to investigate impact time varying phenomena on floating potential a dust grain. The main interest is focused different regimes relevant for RF discharges. Three cases considered. First, case sheath. Second, charging in bulk plasma with electric field and third, when current carried only by fraction electron population. This last low pressure discharges stochastic heating important.
Production of dust particles during tokamak operation is a critical issue for magnetic confinement fusion. Their introduction into the reactor can have serious consequence on its performance and constitute safety issue. For these reasons study in tokamaks crucial. Direct experimental observations such that would give insight their behaviour are quite challenging. In this context, numerical modelling relevant phenomena, plays key role better understanding transport mechanisms tokamaks. work...
Electron emission from the surface of solid particles plays an important role in many dusty plasma phenomena and applications. Examples such cases include fusion plasmas systems our solar system. complicates physics plasma-dust interaction. One most aspects dust interaction is calculation particle's floating potential. This potential a particle acquires when it contact with very for determining its dynamical behaviour. The orbital motion limited (OML) approach used literature to model...
Since the installation on Joint European Torus of ITER-like Wall (ILW), intense radiation spikes have been observed, especially in discharges following a disruption, and associated with possible sudden injection tungsten (W) impurities consequent to full ablation W dust particles. The problem production, mobilization, interaction both plasma vessel tiles is therefore great concern requires setting up dedicated validated numerical modeling tools. Among these, useful role played by trajectory...
Interesting wake effects are found in simulations of dust grains supersonically flowing plasma. A Mach cone is formed at an angle to the flow determined by ratio Bohm speed. The latter well approximated [k(T(e)+γT(i))/m(i)](1/2) with γ=3. For ion temperatures significantly lower than electron temperature, a second (inner) forms due convergence. An "ion vacuum" and stagnation point occur downstream. These cannot be described conventional (cold-ion) gas dynamics. Critically, none cones...
The source–collector sheath system describes a plasma that forms between Maxwellian source and an absorbing wall. is assumed to be collisionless without ionization. Two distinct areas are being formed: the collector sheath, ion-rich region in contact with boundary, which electron-rich area near source. Our work examines effect shifted distributions at have on characteristics of such system. This studied for range drift velocities ratios ion electron temperatures. We study problem both...
The charging of a large dust grain immersed in flowing plasma is important for the study several phenomena and many applications. It shown that order to understand mechanism grains, it great importance take into account calculate effect flows on sheath develops around them.
This paper develops a global model based on non-local properties of fractional derivatives for fusion plasmas. The results confirm that transport in the largest device i.e. JET, is better predicted. expected to provide an insight proper kinetic description plasmas, and improve accuracy predictions.
The diffusion due to collisions with ions of a cloud nano-meter dust particles in the region scrape-off-layer (SOL) tokamak is considered and it shown that for conditions Frascati upgrade, can expand reach SOL limit very short times without ablating. stochastic heating acceleration larger particle hyper-velocities, taking into account effect decreasing density cloud, are established.
In this paper we present a new theory, Modified Orbital Motion Limited - EMission, which examines the effect of electron emission on charging large dust grains. One most important aspects is calculation particle's floating potential, potential that acquires when it in contact with plasma. Our theory determines surface grain and predicts formation well. model applied Dust TOKamakS (DTOKS) transport code compared DTOKS' pre-existing model.