S. Merriman J. Abraham J. Bailey J. Billingsley B. Edwards J. Hagues D. León Hernández N. Mantel N. Otway A. Saigiridhari S. Sherwood P. Ting J. Fradera P. Andrés A. Bernad D. Catalán S. Haouala S. Sádaba B. Echeveste S. Ha
The UK Spherical Tokamak for Energy Production (STEP) program is currently progressing the conceptual engineering design of a Spherical Tokamak-based fusion reactor. The program includes a project concerned with design of the reactor breeding blanket. The objective of this work was to develop a low fidelity, integrated simulation approach to sup…
PreprintDaniel Kennedy Bhavin S Patel Colin M Roach
Microinstabilities often result in turbulence that influences energy confinement in tokamak discharges. One such microinstability, of particular importance to the design of next-generation spherical tokamaks (STs) such as STEP [1], is the microtearing mode (MTM), a tearing-parity mode centred on high-order rational surfaces. MTMs are short-wavel…
PreprintR. Scannell the MAST Upgrade EUROfusion Tokamak Exploitation Teams
MAST Upgrade (MAST-U) is a new low aspect ratio device (R/a = 0.85/0.65 ~ 1.3) based on the MAST tokamak that started plasma operations in October 2020. It has substantial new capabilities compared with the original MAST device, with 19 new poloidal field coils (14 of which are within the vacuum vessel) and new, closed, up-down symmetric diverto…
PreprintHendrik Meyer the STEP Plasma Control Heating & Current Drive Team
With steady progress on ITER project and the design of DEMO, the international community is now entering an era in which fusion power on the grid could become a reality within the next 20 – 30 years. In this environment the UK has started the ambitious Spherical Tokamak for Energy Production (STEP) programme, aiming to develop a compact protot…
PreprintGuoliang Xia T.C. Hender Yueqiang Liu E. Trier
The Spherical Tokamak for Energy Production (STEP) is a UKAEA program that aims to deliver a prototype fusion energy plant and a path to commercial viability of fusion [1]. The low aspect ratio spherical tokamak is attractive because of its potential to achieve high normalized beta βN operation, and the fusion power ~β…
PreprintT. Wilson S.J. Freethy M. Henderson A Köhn-Seeman I. Konoplev S. Saarelma D. Speirs R.G.L. Vann the STEP team
The UK’s Spherical Tokamak for Energy Production (STEP) reactor design program is now exclusively investigating concepts using microwave-based heating and current drive (HCD) systems. Electron Bernstein Wave (EBW) HCD is a relatively immature technology compared to Electron Cyclotron (EC) HCD but is of interest due to the promise of high current…
PreprintK. G. McClements M. Fitzgerald H. J. C. Oliver A. P. Prokopyszyn
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…
PreprintHelen Brooks Andrew Davis
To support the design of fusion reactors for energy production, there is an urgent need to develop highly-scalable multi-physics software tools capable of modelling critical tokamak components as a single cohesive whole. Although some loosely-coupled physics tools do exist, these lack fidelity and will fundamentally fail to capture any closed-lo…
Preprint PublishedJ. Mitchell A. Parrot F. E. Eriksson F. Casson O. Bardsley M. Lennholm H. Meyer S. Aleiferis
In this paper we present optimized actuator trajectories, evolving in time and space, of non-inductive ramp-up scenarios for the Spherical Tokamak for Energy Production (STEP). These trajectories are computed by solving a non-linear, multi-objective, constrained, finite-time optimal control problem. A method unique to STEP ramp-up studies that prov…
Preprint PublishedE. Berger I. Pusztai S.L. Newton M. Hoppe O. Vallhagen A. Fil T. Fülöp
Understanding generation and mitigation of runaway electrons in disruptions is important for the safe operation of future tokamaks. In this paper we investigate runaway dynamics in reactor-scale spherical tokamaks. We study both the severity of runaway generation during unmitigated disruptions, as well as the effect that typical mitigation schem…
Preprint Published