G. McArdle
A5004105429- Magnetic confinement fusion research
- Fusion materials and technologies
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Laser-Plasma Interactions and Diagnostics
- Nuclear reactor physics and engineering
- Nuclear Physics and Applications
- Plasma Diagnostics and Applications
- Advanced Data Storage Technologies
- Solar and Space Plasma Dynamics
- Atomic and Subatomic Physics Research
- Advanced Frequency and Time Standards
- Advanced Image Processing Techniques
- Stability and Control of Uncertain Systems
- NMR spectroscopy and applications
- Laser-induced spectroscopy and plasma
- Electron and X-Ray Spectroscopy Techniques
- Surface and Thin Film Phenomena
- Distributed and Parallel Computing Systems
- Quantum chaos and dynamical systems
- Surface Roughness and Optical Measurements
- Medical Imaging Techniques and Applications
United Kingdom Atomic Energy Authority
1997-2024
Culham Science Centre
2011-2024
Culham Centre for Fusion Energy
2008-2024
Neoclassical magnetic islands are observed to limit the achievable beta in COMPASS-D low collisionality single null divertor tokamak plasmas with ITER-like geometry (R0=0.56 m, B0=1.2 T, Ip=120-180 kA, k=1.6, epsilon =0.3). The limiting is typically well below that expected from ideal instabilities maximum N range of 1.6 2.1. plasma heated up 1.8 MW 60 GHz electron cyclotron resonance heating (ECRH) at second harmonic X mode polarization. time history measured island width compared...
A combination of recently installed state-of-the-art imaging and profile diagnostics, together with established plasma simulation codes, are providing for the first time on Mega Ampère Spherical Tokamak (MAST) tools required studying confinement transport, from core through to edge scrape-off-layer (SOL). The H-mode transport barrier is now routinely turned off using a poloidally localized fuelling fine balancing X-points. Theory, supported by experiment, indicates that radial electric field...
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....
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 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...
The low aspect ratio of the mega amp spherical tokamak (MAST) allows differentiation between different forms H-mode threshold scaling. With optimized fuelling using inboard puffing, and a connected double null divertor (DND) magnetic configuration, power data lie about 1.7 times higher than recent scaling laws. Slight configuration changes, order ion Larmor radius, around DND significantly influence access. confinement in discharges with frequency edge localized modes (ELMs) is generally...
A new diagnostic is developed to reconstruct the plasma boundary using visible wavelength images. Exploiting plasma's edge localized and toroidally symmetric emission profile, a coordinate transform presented from poloidal view image. The reconstruction implemented in MATLAB applied camera images of Mega-Ampere Spherical Tokamak discharges. optically reconstructed boundaries are compared magnetic reconstructions offline code EFIT, showing very good qualitative quantitative agreement. Average...
Several improvements to the MAST plant and diagnostics have facilitated new studies advancing physics basis for ITER DEMO, as well future spherical tokamaks (STs). Using increased heating capabilities P NBI ⩽ 3.8 MW H-mode at I p = 1.2 MA was accessed showing that energy confinement on scales more weakly with strongly B t than in IPB98( y , 2) scaling. Measurements of fuel retention shallow pellets extrapolate an particle throughput 70% its original designed total capacity. The anomalous...
Abstract The Mega Ampère Spherical Tokamak (MAST) programme is strongly focused on addressing key physics issues in preparation for operation of ITER as well providing solutions DEMO design choices. In this regard, MAST has provided results understanding and optimizing H-mode confinement, operating with smaller edge localized modes (ELMs), predicting handling plasma exhaust tailoring auxiliary current drive. all cases, the high-resolution diagnostic capability complemented by sophisticated...
New diagnostic, modelling and plant capability on the Mega Ampère Spherical Tokamak (MAST) have delivered important results in key areas for ITER/DEMO upcoming MAST Upgrade, a step towards future ST devices path to fusion currently under procurement. Micro-stability analysis of pedestal highlights potential roles micro-tearing modes kinetic ballooning formation. Mitigation edge localized (ELM) using resonant magnetic perturbation has been demonstrated toroidal mode numbers n = 3, 4, 6 with...
Abstract Real-time magnetic control has been developed to deliver precise of multiple plasma shape parameters for advanced divertor configurations, including double-null, Super-X, X-point target and X-divertor the first time on MAST Upgrade (MAST-U) spherical tokamak. Successful real-time equilibrium different variables accomplished in 2022–2023 MAST-U experimental campaign configurations. Application boundary reconstruction algorithm, LEMUR, is described compared with off-line diagnostic...
Substantial advances have been made on the Mega Ampère Spherical Tokamak (MAST). The parameter range of MAST confinement database has extended and it now also includes pellet-fuelled discharges. Good pellet retention observed in H-mode discharges without triggering an ELM or H/L transition during peripheral ablation low speed pellets. Co-ordinated studies DIII-D demonstrate a strong link between aspect ratio beta scaling energy confinement, consistent with that obtained when data were merged...
New results from MAST are presented that focus on validating models in order to extrapolate future devices. Measurements during start-up experiments have shown how the bulk ion temperature rise scales with square of reconnecting field. During current ramp-up, not able correctly predict diffusion. Experiments been performed looking at edge and core turbulence. At edge, detailed studies revealed filament characteristics responsible for determining near far scrape off layer density profiles. In...
When resonant magnetic perturbations are applied in MAST, the plasma edge boundary experiences a three-dimensional (3D) distortion, which can be few percent of minor radius amplitude, good agreement with ideal 3D equilibrium modelling. This displacement occurs plasmas both radial position feedback control applied, and without feedback. is employed, an non-axisymmetric field lead to exacerbated due ancillary axisymmetric correction, direction correction dependent upon phase respect toroidal...
Spontaneous transitions from the low “L-mode” to high “H-mode” of tokamak plasma confinement, first observed during neutral beam heating experiments on ASDEX, are now routinely achieved in many experiments. The H-mode regime is attractive as it offers possibility enhanced and thus a route towards more “compact” cost-efficient fusion power-plant. Transition achievable Mega-Amp Spherical Tokamak (MAST) [A. C. Darke et al., Fusion Technology 1994 (Elsevier, Amsterdam, 1995), Vol. 1, p. 799] for...
Low aspect ratio plasmas in devices such as the mega ampere spherical tokamak (MAST) are characterized by strong toroidicity, shaping and self fields, low magnetic field, high beta, large plasma flow intrinsic E × B shear. These characteristics have important effects on behaviour, provide a stringent test of theories scaling laws offer new insight into underlying physical processes, often through amplification present conventional tokamaks (e.g. impact fuelling source geometry H-mode...
The optimisation of scenarios and design real-time-control in tokamaks, especially for machines still phase, requires a comprehensive exploration solutions to the Grad-Shafranov (GS) equation over high-dimensional space plasma coil parameters. Emulators can bypass numerical issues GS equation, if large enough library equilibria is available. We train an ensemble neural networks emulate typical shape-control targets (separatrix at midplane, X-points, divertor strike point, flux expansion,...
<title>Abstract</title> Nuclear fusion could offer clean, abundant energy. However, managing the power exhausted from core plasma towards reactor wall remains a major challenge, compounded in emerging compact designs promising more cost-effective pathways commercial Alternative Divertor Configurations (ADCs) are potential solution. In this work, ADC exhaust control is demonstrated for first time, employing novel method to diagnose neutral gas buffer which shields target. Our work on MAST-U...
Significant progress has been made on the Mega Ampere Spherical Tokamak (MAST) towards a fundamental understanding of transport, stability and edge physics addressing technological issues for future large devices. Collaborative studies L–H transition with NSTX ASDEX Upgrade confirm that operation in connected double-null configuration significantly reduces threshold power, Pthr. The MAST data provide support theory based finite β drift wave turbulence suppression by self-generated zonal...
The paper presents the application of modern computational methods for tokamak plasma control system analysis. Several different approaches feedback controller synthesis are described. General positions robust analysis theory briefly formulated. technique features comparative controllers is presented. these illustrated by example MAST vertical system.