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CCFE-PR(17)192016
An explanation of the observed improvement in H-mode pedestal characteristics with increasing core plasma pressure or poloidal beta, pol b , as observed in MAST and JET, is sought in terms of the impact of the Shafranov shift, D¢ , on ideal ballooning MHD stability. To illustrate this succinctly, a self-consistent treatment of the low magnetic she…
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CCFE-PR(15)602015
The interaction between multiple filamentary plasma eruptions is investigated by modelling the non-linear ideal MHD ballooning mode envelope equation with a mixed Eulerian and Lagrangian characterisation of the boundary conditions. The study of multiple plasma filaments is performed in a specific slab equilibrium susceptible to Rayleigh-Taylor ins…
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CCFE-PR(15)1272015
Prolonged operation of the Joint European Torus (JET) in a set-up involving all ITER partners will be beneficial for ITER. Experiments at JET with its ITER-like wall and using a D–T plasma mixture will help to mitigate risks in the ITER research plan. Training of the ITER operators, technicians and engineers at JET will safe valuable time when IT…
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CCFE-PR(15)452015
The role of anisotropic thermal diffusivity on tearing mode stability is analysed in general toroidal geometry following similar techniques to Glasser et al [A H Glasser, et al, Phys. Fluids 18 (1975) 875], although a stronger ordering of the plasma compressibility is required. Resistive layer equations are obtained for a resistive MHD model with a…
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CCFE-PR(15)302015
Asymmetrical disruptions may occur during ITER operation and they may be accompanied by large sideways forces and rotation of the asymmetry. This is of particular concern because resonance of the rotating asymmetry with the natural frequencies of the vacuum vessel (and other in-vessel components) could lead to large dynamic amplification of the for…
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CCFE-PR(17)222015
The Mega Amp Spherical Tokamak (MAST) is the centre piece of the UK fusion research programme.In 2010, a MAST Upgrade programme was initiated with three primary objectives, to contribute to: (1)testing reactor concepts (in particular exhaust solutions via a flexible divertor allowing Super-X and otherextended leg configurations); (2) adding to the …
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CCFE-PR(15)862015
The theory of tokamak stability to nonlinear “ ballooning ” displacements of elliptical magnetic flux tubes is presented. Above a critical pressure profile the energy stored in the plasma may be lowered by finite (but not infinitesimal) displacements of such tubes (metastability). Above a higher pressure profile, the linear stability boundary, …
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2014
A single chord two-color CO2/HeNe (10.6/0.633 µm) heterodyne laser interferometer has been designed to measure the line integral electron density along the mid-plane of the MAST Upgrade tokamak, with a typical error of 1 × 1018 m-3 (~2 phase error) at 4 MHz temporal resolution. To ensure this diagnostic system can be restored from any failures wi…
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2014
This paper presents two different conceptual designs of neutron cameras for Mega Ampere Spherical Tokamak (MAST) Upgrade. The first one consists of two horizontal cameras, one equatorial and one vertically down-shifted by 65 cm. The second design, viewing the plasma in a poloidal section, also consists of two cameras, one radial and the other one w…
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2014
We investigate the linear theory of the ion-temperature-gradient (ITG) mode, with the goal of developing a general understanding that may be applied to stellarators. We highlight the Wendelstein 7X (W7-X) device. Simple fluid and kinetic models that follow closely from existing literature are reviewed and two new first-principle models are presente…
Showing 61 - 70 of 188 UKAEA Paper Results