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CCFE-PR(15)712015
Electron and ion heating characteristics during merging reconnection startup on the MAST spherical tokamak have been revealed in detail using 130 channel YAG- and 300 channel Ruby-Thomson scattering system and a new 32 chord ion Doppler tomography diagnostic. Detailed 2D profile measurements of electron and ion temperature together with electron de…
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CCFE-PR(15)332015
In this work, we generalise linear magnetohydrodynamic (MHD) stability theory to include equilibrium pressure anisotropy in the uid part of the analysis. A novel `single-adiabatic' (SA) uid closure is presented which is complementary to the usual `double-adiabatic' (CGL) model and has the advantage of naturally reproducing exactly the MHD spectrum …
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2013
Isolated kinks on thermally fluctuating 1/2 111 screw, 100 edge, and 1/2 111 edge dislocations in bcc iron are simulated under zero stress conditions using molecular dynamics (MD). Kinks are seen to perform stochastic motion in a potential landscape that depends on the dislocation character and geometry, and their motion provides fresh insight …
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2012
Frank-Read sources are among the most important examples of dislocation sources in crystals, and their operation facilitates dislocation multiplication and hence yield and plastic flow. Iron is known to become highly elastically-anisotropic as the alpha - gamma transition at 912 degrees centigrage is approached, a temperature regime of critical imp…
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2011
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2011
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2011
We examine a possible mechanism for the formation of protrusions on a metallic surface held in a sufficiently high electric field in the presence of a near-surface void. By means of molecular dynamics simulations we show that the high tensile stress exerted on a Cu f110g surface with a near-surface void can promote the nucleation of dislocations on…
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2010
A prototype neutron camera has been developed and installed at MAST as part of a feasibility study for a multichord neutron camera system with the aim to measure the spatial and time resolved 2.45 MeV neutron emissivity profile. Liquid scintillators coupled to a fast digitizer are used for neutron/ gamma ray digital pulse shape discrimination. The …
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2010
Frank-Read sources are among the most important mechanisms of dislocation multiplication, and their operation signals the onset of yield in crystals. We show that the critical stress required to initiate dislocation production falls dramatically at high elastic anisotropy, irrespective of the mean shear modulus. We hence predict the yield stress of…
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2010
A dislocation segment in a crystal experiences a “self force,” by virtue of the orientation-dependence of its elastic energy. If the crystal is elastically isotropic, this force is manifested as a couple acting to rotate the segment toward the lower energy of the pure screw orientation (i.e. acting to align the dislocation line with its Burgers…
Showing 41 - 50 of 53 UKAEA Paper Results