Supervisor:  Dr Robert Kingham

Title:             Fluid and kinetic modelling of ELM burn-through in tokamak exhaust

Type:             Computational and theoretical

Funding:        50% secured from UKAEA;  other half being sought internally.

This project concerns understanding how to mange the immense heat loads in tokamak exhaust onto the power handling surface – the divertor target – in future reactor-scale tokamaks.  These heat loads are due to “parallel” transport of particles along open field-lines just outside the core, a region known as the scrape-off layer (SOL).  Future fusion reactors will operate in a detached regime, where hot plasma leaving the core and entering the SOL is prevented from coming into contact with the divertor by a cloud of cold neutral gas, since the expected power loads far exceed material limits.  The resilience of the detached configuration to transient power spikes due instabilities such as Edge Localised Modes (ELMs) is a major concern.

Plasma exhaust and divertor detachment is usually modelled using various fluid methods [1]. These methods assume that time scales and length scales of the problem are sufficiently well behaved that well-known transport closures [2] (i.e. for thermal and electrical conductivity), can be used.  However, parallel transport in the SOL can break those assumptions, requiring more involved kinetic modelling [3].  This project intends to explore how kinetic modelling affects the predicted operation and performance of the detached divertor during ELMs, and use this to assess and improve tractable reduced fluid models that can be employed in commonly used 2D fluid codes such as SOLPS to improve accuracy for modelling transients. This project aims to exploit the newly developed ReMKiT1D [4] framework for the construction of fluid and kinetic models of the SOL in 1D.  

This project is in collaboration with UKAEA, who will be supplying 50% of the funding and a co-supervisor based at the Culham Centre for Fusion Energy, in Oxfordshire.  There will be ample opportunity to visit Culham and interact with researchers there.

References:

[1] Dudson, B. D. et al. Plasma Phys. Control. Fusion, 61(6) (2019)

[2] Braginskii, S. I. Reviews of Plasma Physics 1, 205 (1965)

[3] Chankin, A. V. et al. Plasma Phys. Control. Fusion, 60 (2018)

[4] Mijin, S. et al. ReMKiT1D - A framework for building reactive multi- fluid models of the tokamak Scrape-Off Layer with coupled electron kinetics in 1D – submitted to Comp. Phys. Comm. https://arxiv.org/abs/2307.15458