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UKAEA-CCFE-PR(18)452018
In magnetic fusion devices, unwanted non-axisymmetric magnetic eld perturbations, known as error fields (EF), can have detrimental effects on plasma stability and confinement. To minimize their impact on plasma performances and on the available operational space, it is important to identify the EF sources and develop EF control strategies. MAST Up…
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UKAEA-CCFE-PR(18)442018
High-Z impurities in magnetic confinement devices are prone to develop density variations on the fluux-surface, which can significantly affect their transport. In this paper, we generalize earlier analytic stellarator calculations of the neoclassical radial impurity flux in the mixed-collisionality regime (collisional impurity and low-collisionalit…
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UKAEA-CCFE-PR(18)372018
Ultrafast irradiation can drive the electrons in a material out of thermal equilibrium with the nuclei, producing hot, transient electronic states that modify the interatomic potential energy surface. We present, for the first time, a rigorous formulation of two-temperature molecular dynamics that can accommodate these electronic effects in the fo…
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UKAEA-CCFE-PR(18)342018
Tangentially viewing fast camera footage of the low-field side snowflake minus divertor in TCV is analysed across a four point scan in which the proximity of the two X-points is varied systematically. The apparent flow observed in the post-processed movie shows two distinct regions of the camera frame exhibiting differing flow patterns. One flow in…
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UKAEA-CCFE-PR(18)252018
The evolution of the defect microstructure in materials at high temperature is dominated by diffusion-mediated interactions between dislocations, vacancy clusters and surfaces. This gives rise to complex non-linear couplings between interstitial and vacancy-type dislocation loops, cavities and the field of diffusing vacancies that adiabatically fol…
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UKAEA-CCFE-PR(18)112018
Chirping observed in ion cyclotron emission (ICE) from the KSTAR tokamak at sequential proton harmonics in the range 200 to 500 MHz has recently been interpreted (B. Chapman et al., Nucl. Fusion 57, 124004 (2017)) as due to fast, sub-microsecond, evolution of the local deuterium plasma density. This density evolution changes the plasma environment …
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CCFE-PR(17)692017
Density functional theory (DFT) calculations show that self-interstitial atom defects in nonmagnetic body-centred cubic (bcc) metals adopt strongly anisotropic configurations, elongated in the h111i direction1–4. Elastic distortions, associated with such anisotropic defect configurations, appear similar to the distortions around small prismatic d…
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CCFE-PR(17)682017
In many tokamaks ferromagnetic material, usually referred to as an iron-core, is present in order to improve the magnetic coupling between the solenoid and the plasma. The presence of the iron core in proximity to the plasma changes the magnetic topology with consequent e ects on the magnetic field structure and the plasma boundary. This paper cons…
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CCFE-PR(17)652017
Using high speed imaging of the divertor volume, the region close to the X-point in MAST is shown to be quiescent. This is confirmed by three different analysis techniques and the quiescent X-point region (QXR) spans from the separatrix to the N = 1.02 flux surface. Local reductions to the atomic density and effects associated with the camera vie…
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CCFE-PR(17)632017
Experiments have been carried out on the MAST and JET tokamaks intended to compare the electrical resistivity of the plasma with theoretical formulations. The tests consist of obtaining motional stark effect (MSE) measurements in MHD-free plasmas during plasma current ramp-up (JET and MAST), ramp-down (MAST) and in stationary state (JET and MAST). …
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