UKAEA Journals

Showing 21 - 30 of 1620 Journals Results
2020
UKAEA-CCFE-PR(20)141

Using ab initio density function theory calculations, we have determined the structure of self-interstitial atom (SIA) defects in the most commonly occurring face-centred cubic (FCC) metals. The most stable SIA defects in Al, Ca, Ni, Cu, Pd and Ag are the {100} dumbbells whereas octahedral SIA configurations have the lowest energy in Pt, R…

Preprint Published
2020
UKAEA-CCFE-PR(20)140

Finite element analysis (FEA) is widely used in engineering to accurately model physical systems. FEA enables multi-physics investigations to be undertaken efficiently and increases the cohesiveness of interdisciplinary engineering assessments. Thanks to the recent implementation of the FEA Unstructured Mesh capability (UM) into MCNP6, radiation tr…

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The published version of this paper is currently under embargo and will be available on 02/02/2023
2020
UKAEA-CCFE-PR(20)137

Detachment, an important mechanism for reducing target heat deposition, is achieved through reductions in power, particle and momentum; which are induced through plasma-atom and plasma-molecule interactions. Experimental research in how those reactions precisely contribute to detachment is limited. Both plasma-atom as well as plasma-molecule intera…

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The published version of this paper is currently under embargo and will be available on 18/12/2021
2020
UKAEA-CCFE-PR(20)138

The electron runaway phenomenon in plasmas depends sensitively on the momentum space dynamics. However, efficient simulation of the global evolution of systems involving runaway electrons typically requires a reduced fluid description. This is needed for example in the design of essential runaway mitigation methods for tokamaks. In this paper, we p…

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2020
UKAEA-CCFE-PR(20)135

The poloidal harmonics of the toroidal normal modes of an unstable axisymmetric tokamak plasma are employed as basis functions for the minimisation of the 3D energy functional. This approach presents a natural extension of the perturbative method considered in [M.S. Anastopoulos Tzanis et al, Nuclear Fusion 59:126028, 2019]. This variational formul…

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The published version of this paper is currently under embargo and will be available on 21/08/2021
2020
UKAEA-CCFE-PR(20)117

A discrepancy between predicted and measured neutron rates on MAST using TRANSP/NUBEAM was observed. Further causes of this discrepancy are here studied by means of TRANSP/NUBEAM and ASCOT/BBNBI simulations. Gyro-Orbit simulations resulted in an approximately 20 % reduction of the fast ion density compare to the Guiding Center with TRANSP/NUBEAM…

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2019
UKAEA-CCFE-PR(20)120

A Doppler coherence imaging spectroscopy diagnostic has been developed on the HL- 2A tokamak for scrape-off-layer impurity plasma flow measurements. Two- dimensional imaging of line-averaged C2+ flow in the high-field-side scrape off layer with time resolution up to 1 ms, has been achieved successfully by this system. The spatial angular resolut…

Preprint Published
2019
UKAEA-CCFE-PR(20)121

Effects of parallel and poloidal flows, as well as the flow shear, on the resistive wall mode (RWM) instability have been numerically investigated in toroidally rotating plasmas, utilizing a recently updated version of the MARS-F code (Liu Y Q et al 2000 Phys. Plasmas 7 3681). A significant difference between these flow…

Preprint Published
2019
UKAEA-CCFE-PR(20)122

We present an ultrafast neural network (NN) turbulent tokamak transport model, QLKNN, for heat and particle fluxes. QLKNN is a surrogate model based on a database of 3 · 108 flux calculations of the quasilinear gyrokinetic transport model QuaLiKiz. To ensure accurate reproduction of the underlying model, we include known features of the…

Preprint Published