D. Kennedy M. Giacomin B. Patel C. M. Roach D. Dickinson
The importance of parallel magnetic field perturbations in gyrokinetic simulations of electromagnetic instabilities and turbulence at mid-radius in the burning plasma phase of the conceptual high-β, reactor-scale, tight-aspect-ratio tokamak STEP is discussed. Previous studies have revealed the presence of unstable hybrid kinetic ballooning modes (…
PreprintWiera Bielajewa Michelle Tindall Perumal Nithiarasu
Solution reconstruction from limited number of measurements is useful in many areas of heat transfer applications. Unlike the standard problems, such reconstruction problems are ill-posed; thus, the non-uniqueness of solution and inherent instability severely complicates the modelling process. Consequently, more conventional inverse analysis method…
Preprint PublishedWenxing Liu Hanlin Niu Robert Skilton Joaquin Carrasco
When transferring a Deep Reinforcement Learning (DRL) model from simulation to the real world, the performance could be unsatisfactory since the simulation cannot imitate the real world well in many circumstances. This results in a long period of fine-tuning in the real world. This paper proposes a self-supervised vision-based DRL method that al…
PurchaseJ W Berkery S A Sabbagh C Ham V Zamkovska J Butt J Riquezes M Tobin S Henderson L Kogan B Patel R Scannell E Trier B LeBlanc
Fusion power output from spherical tokamaks would benefit from increased confined plasma density, but there exists a limit on the density before confinement is lost and the plasma current is disrupted. This density limit has long been characterized by a simple, global Greenwald limit proportional to the plasma current and inversely proportional …
Preprint PurchaseD. Brunetti J. P. Graves C. J. Ham S. Saarelma
We propose a resistivity-beta driving mechanism aimed at explaining the appearance of free boundary long wavelength global instabilities in high-beta diverted tokamaks. These perturbations resemble very closely the RWM (resistive wall mode) phenomenon. Performing a proper toroidal analysis, we show that the magnetohydrodynamic stability is worsened…
PreprintValentine Kanyanta
Fusion is considered as one of the most attractive carbon-free energy sources with the potential to play a vital role in meeting long-term global energy needs. Research into fusion has accelerated over the past few years with more participation now seen from the private sector. Fusion is making an important transition from fundamental research t…
PreprintR. B. Morales A. Salmi P. Abreu C. H. S. Amador P. Carman J. Fessey J. Flanagan M. Fontana C. Giroud S. Hacquin S. Heuraux L. Meneses R. Sabot A. Silva A. Sirinelli G. Szepesi D. Taylor D. Terranova
JET’s frequency-modulated continuous-wave (FMCW) reflectometers have been operating well with the current design since 2005 and density profiles are being automatically calculated intershot since then[1]. However, the calculated profiles had long suffered from several shortcomings – poor agreement to other diagnostics; sometimes inappropriat…
PreprintAnder Gray Scott Ferson Edoardo Patelli
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.…
Preprint PublishedC. Cowley Bruce Lipschultz David Moulton Ben Dudson
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…
Preprint PublishedR. Scannell J. G. Clark Y. Kim D. Kos M. Maslov L. Giudicotti
Thomson scattered light is polarised in the same orientation as the incident laser beam at low electron temperatures. At high temperatures (>~4keV) part of the spectrum begins to become randomly polarised. First measurement of the depolarised Thomson scattering spectrum during were obtained from JET pulses 92038-92504. This paper builds upon …
Preprint Published