A5030835377- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Laser-Plasma Interactions and Diagnostics
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Solar and Space Plasma Dynamics
- Laser-induced spectroscopy and plasma
- Plasma Diagnostics and Applications
- Nuclear reactor physics and engineering
- Calibration and Measurement Techniques
- Atomic and Subatomic Physics Research
- Astronomical Observations and Instrumentation
- Aerodynamics and Fluid Dynamics Research
- Semiconductor Lasers and Optical Devices
- Photonic and Optical Devices
- Astro and Planetary Science
- Atomic and Molecular Physics
- Nuclear Physics and Applications
- Spectroscopy Techniques in Biomedical and Chemical Research
- Tropical and Extratropical Cyclones Research
- Optical Systems and Laser Technology
- Surface Roughness and Optical Measurements
- Physics of Superconductivity and Magnetism
- Inertial Sensor and Navigation
Culham Centre for Fusion Energy
2011-2024
Culham Science Centre
2015-2024
United Kingdom Atomic Energy Authority
2018-2024
Royal Military Academy
2020
Durham University
2014
University College Cork
2004-2007
Plasma equilibria reconstructed from the Mega-Amp Spherical Tokamak have sufficient resolution to capture plasma evolution during short period between edge-localized modes (ELMs). Immediately after ELM, steep gradients in pressure, $P$, and density, ${n}_{e}$, form pedestals close separatrix, they then expand into core. Local gyrokinetic analysis over ELM cycle reveals dominant microinstabilities at perpendicular wavelengths of order ion Larmor radius. These are kinetic ballooning pedestal...
Edge-localized modes (ELMs) are repetitive instabilities that occur in the outer region of tokamak plasmas. This Letter provides new information on and implications evolution filament structures observed during ELMs MAST tokamak. The filaments exist for time over which particles being released into scrape off layer. They start at plasma edge rotating velocity pedestal, then decelerate toroidally accelerate radially outwards. As propagate they remain aligned with local magnetic field line.
The boundary of the tokamak core plasma, or scrape-off layer, is normally characterized in terms average parameters such as density, temperature and e-folding lengths suggesting diffusive losses. However, shown this paper, localized filamentary structures play an important role determining radial efflux both L mode during edge modes (ELMs) on MAST. Understanding size, poloidal toroidal localization outward extent these filaments crucial order to calculate their effect power loading first...
The instrument function of the high resolution Thomson scattering (HRTS) diagnostic in Joint European Torus (JET) has been calculated for use improved pedestal profile analysis. full width at half maximum (FWHM) spatial response is (22 ± 1) mm original HRTS system configuration and depends on particular magnetic topology JET plasmas. An improvement to optical design laser input presented. smearing across flux surfaces reduced this design. new implemented (from JPN 78742, July 2009)...
Sustained edge-localized mode (ELM) mitigation has been achieved using resonant magnetic perturbations (RMPs) with a toroidal number of n = 4 and 6 in lower single null 3 connected double plasmas on MAST. The ELM frequency increases by up to factor eight similar reduction energy loss. A threshold current for is observed above which the approximately linearly coils. comparison filament structures during ELMs natural mitigated stages shows that have characteristics type I even though their...
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation M. N. A. Beurskens, T. H. Osborne, P. Schneider, E. Wolfrum, L. Frassinetti, R. Groebner, Lomas, I. Nunes, S. Saarelma, Scannell, B. Snyder, D. Zarzoso, Balboa, Bray, Brix, J. Flanagan, C. Giroud, Giovannozzi, Kempenaars, Loarte, de la Luna, G. Maddison, F. Maggi, McDonald, Pasqualotto, Saibene, Sartori, Emilia...
Type I ELMy H-mode operation in JET with the ITER-like Be/W wall (JET-ILW) generally occurs at lower pedestal pressures compared to those full carbon (JET-C). The density is similar but temperature where type ELMs occur reduced and below so-called critical I–type III transition reported JET-C experiments. Furthermore, confinement factor H98(y,2) baseline plasmas JET-ILW low power fractions Ploss/Pthr,08 < 2 (where Ploss (Pin − dW/dt), Pthr,08 L–H threshold from Martin et al 2008 (J. Phys....
We present the first analysis of atomic and molecular processes at play during detachment in MAST-U Super-X divertor using spectroscopy data. Our indicates can be separated into four sequential phases: First, ionisation region detaches from target onset leaving a increased densities downstream. The plasma interacts with these molecules, resulting ions ($D_2^+$ and/or $D_2^- \rightarrow D + D^-$) that further react leading to Molecular Activated Recombination Dissociation (MAR MAD), which...
Pedestal profiles that span the ELM cycle have been obtained and used to test idea pedestal pressure gradient in MAST is limited by onset of kinetic ballooning modes (KBMs). During inter-ELM period a regularly type I ELM-ing discharge on MAST, height width increase together while increases only 15% during cycle. Stability analyses show region over which infinite-n are unstable also broadens To relationship between n = ∞ ideal magnetohydrodynamic KBMs gyrokinetic code, GS2, has for...
A new infrared Thomson scattering system has been designed for the MAST tokamak. The will measure at 120 spatial points with ≈10 mm resolution across plasma. Eight 30 Hz 1.6 J Nd:YAG lasers be combined to produce a sampling rate of 240 Hz. follow separate parallel beam paths vessel. Scattered light collected approximately f/6 over angles ranging from 80° 120°. laser energy and lens size, relative an existing 1.2 f/12 system, greatly increases number scattered photons per unit length beam....
A factor of 4 dimensionless collisionality scan H-mode plasmas in MAST shows that the thermal energy confinement time scales as . Local heat transport is dominated by electrons and consistent with global scaling. The neutron rate good agreement ν* dependence τE,th. gyrokinetic code GYRO indicates micro-tearing turbulence might explain such a trend. 1.4 safety These two scalings are on plasma current magnetic field. Weaker qeng stronger dependences compared IPB98y2 scaling could be favourable...
Recently, the TS-3 and TS-4 tokamak merging experiments revealed significant plasma heating during magnetic reconnection. A key question is how where ions electrons are heated Two-dimensional measurements of ion electron temperatures flow made clear that inside current sheet mainly by Ohmic in downstream areas reconnection outflows. The outflow kinetic energy thermalized fast shock formation viscous damping. converts reconnecting field mostly to thermal region whose size much larger than for...
Microtearing modes (MTMs) are unstable in the shallow gradient region just inside top of pedestal spherical tokamak experiment MAST, and may play an important role evolution. The linear properties these instabilities compared with MTMs deeper core, further detailed investigations s–α geometry expose basic drive mechanism, which is not well described by existing theories. In particular, growth rate dominant edge MTM does peak at a finite collision frequency, as frequently reported for into...
Sustained edge localized mode (ELM) mitigation has been achieved on MAST and AUG using resonant magnetic perturbations (RMPs) with various toroidal numbers over a wide range of low to medium collisionality discharges. The ELM energy loss peak heat loads at the divertor targets have reduced. phase is typically associated drop in plasma density overall stored energy. In one particular scenario MAST, by carefully adjusting fuelling it possible counteract produce plasmas mitigated ELMs, reduced...
Abstract The EUROfusion JET-ILW pedestal database is described, with emphasis on three main issues. First, the technical aspects are introduced, including a description of data selection, datasets, diagnostics used, experimental and theoretical methods implemented definitions. Second, structure stability described. In particular, work describes links between engineering parameters (power, gas divertor configuration) disagreement peeling-ballooning (PB) model ideal magnetohydrodynamics...
Abstract The integration of good core and edge/pedestal confinement with strong dissipation heat particles in the divertors is a significant challenge for development fusion energy. Alternative divertor configurations offer potential advantages by broadening operational space where device can operate detached acceptable power exhaust. First results from MAST Upgrade are presented high mode experiments outer Super-X configuration, showing that naturally detach when formed no discernible...
Studies of the pedestal characteristics and quantities determining edge-localized mode (ELM) energy losses in MAST are presented. High temperature plasmas have been achieved which collisionalities one order magnitude lower than previous results . A stability analysis performed on these shows them to be near ballooning limit. The fraction released by an ELM as a function collisionality is consistent with data from other devices. evolution filamentary structures observed during ELMs has...
A Thomson scattering diagnostic designed to measure both edge and core physics has been implemented on MAST. The system uses eight Nd:YAG lasers, each with a repetition rate of 30 Hz. relative absolute timing the lasers may be set arbitrarily produce fast bursts measurements suit time evolution being studied. scattered light is collected at F/6 by 100 kg six element lens an aperture stop 290 mm. then transferred 130 polychromators independent fiber bundles. data acquisition processing are...
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 distortion of the plasma boundary when three-dimensional resonant magnetic perturbations (RMPs) are applied has been measured in MAST H-mode plasmas. When n = 3 RMPs to control edge-localized modes (ELMs), experiences a strong toroidal corrugation. displacement is at various locations and found be order 5% minor radius for an field magnitude which mitigates ELMs. empirically observed corrugation edge position agrees well with ideal equilibrium reconstruction.
In DT plasmas, toroidal Alfvén eigenmodes (TAEs) can be made unstable by the alpha particles resulting from fusion reactions, and may induce a significant redistribution of fast ions. Recent experiments have been conducted in JET deuterium plasmas order to prepare scenarios aimed at observing alpha-driven TAEs future campaign. Discharges low density, large core temperatures associated with presence internal transport barriers characterised good energetic ion confinement performed. ICRH has...
Thomson scattering measurements with subcentimeter spatial resolution have been made during a sawtooth crash in Mega Ampere Spherical Tokamak fusion plasma. The unparalleled of the temperature profile has shed new light on mechanisms that underlie sawtooth. As magnetic reconnection occurs, gradient at island boundary increases. increased local is sufficient to make helical core unstable ideal magnetohydrodynamic instabilities, thought be responsible for rapidity collapse.
The H-mode pedestal characteristics on MAST are measured in a variety of connected double null (CDN) and single divertor (SND) discharges. In CDN discharges the edge density width spatial co-ordinates is similar both high low field sides suggesting that may be determined by neutral penetration. However, SND appears to flux surface quantity, which suggests scrape-off-layer have role play determining width. temperature quantity. stability been studied as function ELM type. found weak...