A. R. Field
A5064333742- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Solar and Space Plasma Dynamics
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Nuclear reactor physics and engineering
- Laser-induced spectroscopy and plasma
- Meteorological Phenomena and Simulations
- Nuclear Physics and Applications
- Spectroscopy and Laser Applications
- Particle Accelerators and Free-Electron Lasers
- Nuclear Materials and Properties
- Atomic and Subatomic Physics Research
- GNSS positioning and interference
- Atomic and Molecular Physics
- Quantum Chromodynamics and Particle Interactions
- Advanced Data Storage Technologies
- High-pressure geophysics and materials
- Nuclear Engineering Thermal-Hydraulics
- Spacecraft and Cryogenic Technologies
- Quantum chaos and dynamical systems
- Computer Graphics and Visualization Techniques
Culham Science Centre
2014-2024
National Agency for New Technologies, Energy and Sustainable Economic Development
2024
United Kingdom Atomic Energy Authority
2021-2024
Culham Centre for Fusion Energy
2008-2023
Fusion Academy
2019
Higashihiroshima Medical Center
2006
Hiroshima University
2006
Lawrence Livermore National Laboratory
2006
University of California, Irvine
2006
University of Washington
2006
MAST plasmas with a safety factor above unity and profile either weakly reversed shear or broad low-shear regions, regularly exhibit long-lived saturated ideal magnetohydrodynamic (MHD) instabilities. The toroidal rotation is flattened in the presence of such perturbations fast ion losses are enhanced. These modes, distinguished as by notable lack islands signs reconnection, driven unstable approaches unity. This could be significance for advanced scenarios, hybrid scenarios which aim to...
Abstract The JET hybrid scenario has been developed from low plasma current carbon wall discharges to the record-breaking Deuterium-Tritium plasmas obtained in 2021 with ITER-like Be/W wall. development started pure Deuterium refinement of current, and toroidal magnetic field choices succeeded solving heat load challenges arising 37 MW injected power ITER like environment, keeping radiation edge core controlled, avoiding MHD instabilities reaching high neutron rates. have re-run Tritium...
Several experiments were conducted in ASDEX Upgrade to prove the suitability of tungsten as a divertor target material under conditions high density and low temperature divertor. The observed fluxes from tile into plasma are low, keeping with extremely sputtering yields. In addition, very favourable effect `prompt redeposition' (redeposition during first gyration) could be confirmed by experiments. Cooling edge region neon injection seems permissible, i.e. impurity did not increase eroded...
Feedback-controlled puffing of neon and deuterium has been applied to control the edge-localized-mode behavior target plate power deposition during high-power $H$-mode discharges in ASDEX Upgrade. A regime found which more than 90% heating is lost through radiation divertor detachment occurs, without deterioration energy confinement. The plasma remains $H$ mode, exhibiting small-amplitude, high-frequency ELM's, do not penetrate plates strike zone region.
Values of ${\ensuremath{\beta}}_{T}\ensuremath{\ge}30%$ have been achieved and sustained for several confinement times on the START spherical tokamak using additional heating provided by neutral beam injection. These values are more than twice highest value previously obtained in a tokamak, correspond to normalized $\ensuremath{\beta}$ ${\ensuremath{\beta}}_{N}\ensuremath{\ge}4$. In these shots ${I}_{p}>{I}_{\mathrm{rod}}$ (where ${I}_{\mathrm{rod}}$ is current flowing central toroidal field...
Recent experiments (Synakowski et al 2004 Nucl. Fusion 43 1648, Lloyd Plasma Phys. Control. 46 B477) on the Spherical Tokamak (or Torus, ST) (Peng 2000 Plasmas 7 1681) have discovered robust plasma conditions, easing shaping, stability limits, energy confinement, self-driven current and sustainment. This progress has encouraged an update of conditions engineering a Component Test Facility (CTF), (Cheng 1998 Eng. Des. 38 219) which is very valuable step in development practical fusion energy....
This paper reviews transport and confinement in spherical tokamaks (STs) our current physics understanding of this that is partly based on gyrokinetic simulations. Equilibrium flow shear plays an important role, we show how consistently included the framework for flows greatly exceed diamagnetic velocity. The key geometry factors influence effectiveness turbulence suppression by are discussed, toroidal equilibrium can sometimes entirely suppress ion scale today's STs. Advanced nonlinear...
This paper compares the gyrokinetic instabilities and transport in two representative JET pedestals, one (pulse 78697) from configuration with a carbon wall (C) another 92432) after installation of JET's ITER-like Wall (ILW).The discharges were selected for comparison JET-ILW JET-C good confinement at high current (3 MA, corresponding also to low ρ * ) retain distinguishing features JET-ILW, notably, decreased pedestal top temperature JET-ILW.A profiles heating power reveals stark...
Abstract We present the results of GENE gyrokinetic calculations based on a series JET–ITER-like-wall (ILW) type I ELMy H-mode discharges operating with similar experimental inputs but at different levels power and gas fuelling. show that turbulence due to electron-temperature-gradient (ETGs) modes produces significant amount heat flux in four JET–ILW discharges, and, when combined neoclassical simulations, is able reproduce for two low pulses. The simulations plausibly high-gas fluxes as...
Abstract The work describes the pedestal structure, transport and stability in an effective mass ( A eff ) scan from pure deuterium to tritium plasmas using a type I ELMy H-mode dataset which key parameters that affect behaviour (normalized pressure, ratio of separatrix density density, ion Larmor radius, collisionality rotation) are kept as constant possible. Experimental results show significant increase at top with increasing , modest reduction temperature pressure. variations heights...
Abstract The influence of rotation, collisionality and trapped particle fraction on the magnitude direction neoclassical impurity transport in tokamaks is analyzed using an extensive database drift-kinetic simulations with NEO code. It shown that operational window opens at sufficiently high Mach number low collisionality, where temperature screening impurities increases higher rotation. If increases, this effect quickly lost gradient then drives inward flux when rotation present. boundary...
Puffing of impurities (neon, argon) and deuterium gas in the main chamber is used to feedback control total radiated power fraction divertor neutral particle density simultaneously ASDEX Upgrade tokamak. The variation Psep=Pheat-Prad(core) by impurity radiation during H mode shows a similar effect on ELM behaviour as that obtained change heating power. For fractions above 90%, amplitude becomes very small detachment from plates occurs, whilst no degradation global energy confinement observed...
A predictive model for the electron temperature profile of H-mode pedestal is described, and its results are compared with structure JET-ILW plasmas. The based on a scaling gyro-Bohm normalized, turbulent heat flux [Formula: see text] resulting from gradient (ETG) turbulence, derived nonlinear gyrokinetic (GK) calculations steep region. By using local scale length in normalization, dependence normalized gradients can be represented by unified parameter text], to which linear stability ETG...
Abstract Plasma turbulence on disparate spatial and temporal scales plays a key role in defining the level of confinement achievable tokamaks, with development reduced numerical models for cross-scale effects informed by experimental measurements an essential step. MAST-U is well-equipped facility having instruments to measure ion electron scale at plasma edge. However, measurement core challenging, especially H mode. Using novel synthetic diagnostic approach, we present simulated...
Abstract JET returned to deuterium-tritium operations in 2023 (DTE3 campaign), approximately two years after DTE2. DTE3 was designed as an extension of JET's 2022-2023 deuterium campaigns, which focused on developing scenarios for ITER and DEMO, integrating in-depth physics understanding control schemes. These were evaluated with mixed D-T fuel, using the only remaining tritium-capable tokamak until its closure 2023. A core-edge-SOL integrated H-mode scenario developed tested D-T, showing...
This paper presents a description of the spatial and temporal structure edge-localized modes (ELMs) observed in MAST tokamak. Filamentary enhancements visible light are on photographic images plasma obtained during ELMs. Comparisons with simulations show that these filaments consistent following field lines at outboard edge plasma. The toroidal mode number has been extracted from study discrete peaks ion saturation current recorded by mid-plane reciprocating probe. A time delay respect to...
The completely detached high confinement (CDH) regime established recently in power ASDEX-Upgrade single null divertor discharges is described. standard CDH mode scenario with feedback controlled external deuterium and neon puffing analysed detail respect to its detachment properties. Impurity transport pumping effects the density operation windows of are outlined. First results other impurity radiators (N,Ar) given. Finally space discussed terms main chamber scrape-off layer plus radiation...
Major developments on the Mega Amp Spherical Tokamak (MAST) have enabled important advances in support of ITER and physics basis a spherical tokamak (ST) based component test facility (CTF), as well providing new insight into underlying physics. For example, L–H transition studies benefit from high spatial temporal resolution measurements pedestal profile evolution (temperature, density radial electric field) stability edge current has been inferred motional Stark effect measurements. The...
The high-k () wavenumber spectrum of density fluctuations has been measured for the first time in MAST (Lloyd et al 2003 Nucl. Fusion 43 1665). This was accomplished with implementation Doppler backscattering (DBS) core measurements a spherical tokamak. DBS become well-established and versatile diagnostic technique measurement intermediate- k (, higher) flows magnetically confined fusion experiments. Previous implementations have standard, large aspect ratio tokamaks. A novel two-dimensional...
The mega amp spherical tokamak (MAST) was a low aspect ratio device (R/a = 0.85/0.65 ~ 1.3) with similar poloidal cross-section to other medium-size tokamaks. physics programme concentrates on addressing key issues for the operation of ITER, design DEMO and future tokamaks by utilising high resolution diagnostic measurements closely coupled theory modelling significantly advance our understanding. An empirical scaling energy confinement time that favours higher power, lower collisionality...
Abstract A reduction of the pedestal pressure with increasing separatrix density over ( n e sep / ped ) has been observed in JET. The physics behind this correlation is investigated. due to two distinct mechanisms. increase till ≈0.4 shifts radially outwards, decreasing peeling-balloning stability and reducing height. effect position saturates above ≈ 0.4. For higher values, ascribed increased turbulent transport and, likely, resistive MHD effects. reduces ∇ /n , η transport. This gradient...
Abstract Screening of high-Z (W) impurities from the confined plasma by temperature gradient at periphery fusion-grade H-mode plasmas has been demonstrated in JET-ILW (ITER-like wall) tokamak. Through careful optimisation hybrid-scenario, deuterium with sufficient heating power ( <?CDATA $\gtrsim$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>≳</mml:mo> </mml:math> 32 MW), high enough ion gradients pedestal top can be achieved for collisional,...
The major objective of the National Spherical Torus Experiment (NSTX) is to understand basic toroidal confinement physics at low aspect ratio and high βT in order advance spherical torus (ST) concept. In do this, NSTX utilizes up 7.5 MW neutral beam injection, 6 harmonic fast waves (HHFWs), it operates with plasma currents 1.5 MA elongations 2.6 a field 0.45 T. New facility, diagnostic modelling capabilities developed over past two years have enabled research team make significant progress...
An avalanche photodiode based (APD) detector for the visible wavelength range was developed low light level, high frequency beam emission spectroscopy (BES) experiments in fusion plasmas. This solid state has higher quantum efficiency than photomultiplier tubes, and unlike normal photodiodes, it internal gain. paper describes as well noise model of electronic circuit. By understanding sources amplification process, optimal amplifier APD reverse voltage setting can be determined, where...
Neo-classical tokamak plasma theory predicts poloidal rotation driven by the temperature gradient of a few km s−1. In conventional aspect-ratio plasmas, e.g. on JET and DIII-D, apparent velocities considerably in excess neo-classical values have been measured, particularly presence internal transport barriers, means charge-exchange recombination spectroscopy (CXRS) fully ionized C6+ impurity ions. Comparison between such measurements theoretical predictions requires careful corrections to be...