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Thursday 30 Jan 2020Challenges for modelling fusion plasmas

Dr. Wayne Arter - UKAEA

Harrison 170 14:30-15:30


Modelling fusion plasmas presents many challenges, so that it is reasonable that many modelling codes still use simple finite difference representations that make it relatively easy to explore new physical processes and preserve numerical stability [1]. However, October 2019 announcements by UK government have given UKAEA the challenge of designing a nuclear fusion reactor in the next 5 years, plus a funding element for upgrading existing software both for Exascale and to meet the design challenge. The biggest modelling problem is still that of turbulence mostly at relatively low plasma collisionality. The referent equations are Maxwell-Boltzmann, for which many different numerical representations, exploiting low collisonality and the presence of a strong, directed magnetic field have been explored [2]. One such is ideal MHD, where I have explored the use of the Lie derivative [3, 4]. Some further speculations as to the likely role of Lie techniques in solving Vlasov-Maxwell and its approximations might be presented. One option under examination is the use of high order 'spectrally accurate' elements, to exploit emerging computer architectures and to track numerical errors. There is also need to identify uncertainties in the modelling process, whilst providing a consistent treatment of interactions between the different approximations used for the plasma dynamics, which range over different scales and dimensions. Details of the approach to modelling in the Exascale era proposed by UKAEA will be presented. This work was funded by the RCUK Energy Programme and the European Communities under the contract of Association between EURATOM and CCFE.

[1] B.D. Dudson, A. Allen, G. Breyiannis, E. Brugger, J. Buchanan, L. Easy, S. Farley, I. Joseph,

M. Kim, A.D. McGann, et al. BOUT++: Recent and current developments. Journal of Plasma

Physics, 81(01):365810104, 2015.

[2] W. Arter. Numerical simulation of magnetic fusion plasmas. Reports on Progress in Physics,

58:1{59, 1995.

[3] W. Arter. Potential Vorticity Formulation of Compressible Magwnetohydrodynamics. Physical

Review Letters, 110(1):015004, 2013.

[4] W. Arter. Beyond Linear Fields: the Lie-Taylor Expansion. Proc Roy Soc A, 473:20160525, 2017.

Bio: Wayne Arter, MMath, PhD, recently upgraded to SMIEEE on the basis of work designing relativistic magnetrons in the late 1990s and for the SMARDDA software. In the former case, he was also involved in developing the body-fitted electromagnetic PIC software used in the design. In the latter, he has been lead author of a suite of software modules which has been principally used to model heat deposition on the first wall of many different tokamak fusion experiments to validate surface designs. His other interests include uncertainty quantification and nonlinear dynamics. Currently he is mainly working on the Excalibur project, which he will touch upon in the talk.

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