Open AccessFusion performance of spherical and conventional tokamaks: implications for compact pilot plants and reactors
Author(s) -
A. E. Costley,
Steven McNamara
Publication year - 2021
Publication title -
plasma physics and controlled fusion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.328
H-Index - 111
eISSN - 1361-6587
pISSN - 0741-3335
DOI - 10.1088/1361-6587/abcdfc
Subject(s) - tokamak , spherical tokamak , fusion , fusion power , nuclear engineering , plasma , toroid , magnetic confinement fusion , nuclear fusion , physics , power (physics) , computational physics , toroidal field , beta (programming language) , nuclear physics , computer science , thermodynamics , linguistics , philosophy , engineering , programming language
Spherical tokamaks (STs) have features that make them a potentially attractive option for fusion power production compared to conventional tokamaks (CTs) including operation at high beta and high self-driven ‘bootstrap’ current. The thermal energy confinement time ( τ Ε ) also typically has a stronger dependence on toroidal magnetic field and a weaker dependence on plasma current, but so far it has not been established how this difference impacts performance under reactor conditions. This aspect is explored in this paper. Using empirical data from NSTX and MAST, and from multiple CTs, we investigate analytically and by using established fusion codes the potential fusion performance, characterised by the fusion triple product, nTτ Ε , and fusion power gain, Q fus , where n and T are the density and temperature respectively. We find that for similar values of field and fusion power, but smaller volume, STs can have nTτ Ε up to a factor of three higher and Q fus an order of magnitude higher than CTs. We identify the origin of this enhanced performance and outline a measurement to advance this finding. Potentially our results open an alternative and faster route to fusion power based on relatively small, low power STs.