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UKAEA-CCFE-PR(22)622022
We have devised a new type of feedforward neural network. It is equivariant with respect to unitary operators $U(n)$. The input and output can be vectors in $\\mathbb{C}^n$ with arbitrary dimension~$n$. No convolution layer is required in our implementation, and we also avoid errors due to truncated higher order terms in Fourier-like transformat…
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UKAEA-CCFE-PR(22)612022
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UKAEA-CCFE-PR(22)602022
This work was carried out to identify sources of errors, uncertainties and discrepancies in studies of fuel retention in wall components from the JET tokamak using methods based on thermal desorption. The parallel aim was to establish good practices in measurements and to unify procedures in data handling. A comprehensive program designed for deute…
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UKAEA-CCFE-PR(22)592022
Sequential numerical methods for integrating initial value problems (IVPs) can be prohibitively expensive when high numerical accuracy is required over the entire interval of integration. One remedy is to integrate in a parallel fashion, “predicting” the solution serially using a cheap (coarse) solver and “correcting” these values using an …
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UKAEA-CCFE-PR(22)572022
The LOCUST GPU code has been applied to study the fast-ion transport caused by resonant magnetic perturbations in the high-performance Q = 10 ITER baseline scenario. The computational speed of the code is used calculate the impact of the ITER ELM-control-coil system on neutral beam heating efficiency, as well as producing detailed predictions o…
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UKAEA-CCFE-PR(22)582022
Elementary formulas for propagating information about means and variances through mathematical expressions have long been used by analysts. Yet the precise implications of such information are rarely articulated. This paper explores distribution-free techniques for risk analysis that do not require simulation, sampling or approximation of any kind.…
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UKAEA-CCFE-PR(22)642022
Ion cyclotron emission (ICE) originating from confined populations of fast ions in toroidal fusion plasmas is an important non-invasive, passive diagnostic for current and next generation devices. The ability to model the ICE signals accurately is an essential step towards inferring the characteristics of confined energetic alpha-particles or fast …
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UKAEA-CCFE-PR(22)562022
Parareal is a well-studied algorithm for numerically integrating systems of time-dependent differential equations by parallelising the temporal domain. Given some initial values at each temporal sub-interval, the algorithm iteratively locates a solution in a fixed number of iterations using a predictor-corrector, stopping once a tolerance is met. T…
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UKAEA-CCFE-PR(22)552022
The MAST-U fusion plasma research device, the upgrade to the Mega Amp Spherical Tokamak, has recently completed its first campaign of physics operation. MAST-U operated with Ohmic, or one or two neutral beams for heating, at 400-800 kA plasma current, in conventional or “SuperX” divertor configurations. Equilibrium reconstructions provide key p…
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UKAEA-CCFE-PR(22)542022
As tokamak research moves to reactor conditions, the control of a stable, optimally-detached divertor plasma has become increasingly relevant. Simple predictions of such detachment control have been performed previously using the Detachment Location Sensitivity (DLS) model of detachment. In this study the DLS model is extended and combined with SOL…
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