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UKAEA-STEP-PR(23)012023
In this work, the MARS-F/K codes (Liu Y Q et al 2000 Phys. Plasmas 7 3681 & Liu Y Q et al 2008 Phys. Plasmas 15 112503) are utilized to model the passive and active control of the n=1 (n is the toroidal mode number) resistive wall mode (RWM) in a spherical tokamak (aspect rat…
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UKAEA-CCFE-PR(23)1282022
Predictions of the impact of charge-exchange (CX) reactions on beam ions in the MAST Upgrade spherical tokamak have been compared to measurements carried out with a fission chamber (neutron fluxes) and a Fast Ion Deuterium-Alpha (FIDA) diagnostic. A simple model was developed to reconstruct the outer-midplane neutral density based on Thomson sca…
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UKAEA-CCFE-CP(23)442022
Due to their relatively higher Vbeam/VAlvén ratio, spherical tokamaks are ideal to investigate high-frequency modes such as Compressional Alfvén Eigenmodes (CAEs) and Global Alfvén Eigenmodes (GAEs), and so they have been previously studied in MAST [1, 2]. Besides, the recently installed scintillator-based Fast-Ion Loss …
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UKAEA-STEP-CP(23)042022
The UK has launched a programme to build a prototype fusion power plant, the Spherical Tokamak for Energy Production (STEP), by 2040. It is intended that the STEP prototype will generate fusion power of the order of 1 GW and net electrical power of the order of 100 MW. Plasma scenarios that could be compatible with these design requirements and wit…
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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)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-CP(23)302021
Many of the essential data analysis procedures for a tokamak experiment rely on the knowledge of the magnetic field structure obtained from MHD force balance. On JET, the code that is responsible for computing the magnetic equilibrium is called EFIT++. Interpretation of JET data has been challenging due to inconsistencies between diagnostic meas…
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UKAEA-CCFE-PR(21)302021
Recent JET Deuterium experiments with an advanced internal transport barrier (ITB) scenario have been performed to clearly observe destabilised toroidicity-induced Alfvén eigenmodes (TAEs) by fast ions; interestingly, these also exhibit unstable electromagnetic (EM) perturbations in the sub-TAE frequency range. We identify such EM perturbations to…
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UKAEA-CCFE-PR(21)232021
The work reported in this paper has already been presented internally by placement student Jacob Young at a MAST Physics and Technology meeting on December 17 2020. Therefore it does not require a paper review presentation. Please also note that the paper is proposed for inclusion in a special issue of Plasma Research Express linked to the recent I…
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UKAEA-CCFE-PR(23)832020
Observations have recently been made of ion cyclotron emission (ICE) that originates from the core plasma in the DIII-D and ASDEX-Upgrade tokamaks. In some of these cases, the ICE spectral peaks correspond to the local cyclotron harmonic frequencies of fusion-born ions close to the magnetic axis. This is in contrast to the hitherto usual spatial lo…
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