Abstract
We present the first parallel electron transport results obtained using the newly developed 1D transport code SOL-KiT. With the capability to switch between consistent kinetic and fluid models for the electrons, we explore and report the differences in both equilibrium and transient simulations. Significant kinetic effects are found during transients, especially in the behaviour of the electron sheath heat transmission coefficient, which shows up to an eightfold increase. Equilibria are obtained for an input power scan with parameters relevant to medium size tokamaks. Detached equilibria are found to persist to higher input powers when electrons are treated kinetically. Furthermore, non-monotonic behaviour of the electron sheath heat transmission coefficient is observed in the power scan, with values being up to 40% above the classical value. We discuss the implications of the presented results to potential modelling decisions, as well as possible extensions to the used model.
Highlights
The Scrape-Off Layer (SOL) is the region of open field lines in Magnetically Confined Fusion devices, through which the energy and particles which escape the fusion core travel to the plasma-facing components of the reactor
We have presented in this study both equilibrium and transient simulations of parallel electron transport in the SOL, treating the electrons as either a fluid or kinetically
It is found that it is non-negligible even for the lowest power equilibria. Another equilibrium kinetic effect that has been explored here is the modification of the electron sheath heat transmission coefficient, where we find up to ≈ 40% variation with respect to the assumed classical fluid value of γe≈ 5
Summary
The Scrape-Off Layer (SOL) is the region of open field lines in Magnetically Confined Fusion devices, through which the energy and particles which escape the fusion core travel to the plasma-facing components of the reactor. Previous numerical studies of kinetic effects in the SOL have been performed with a wide array of codes, including both PIC [5, 6] and finite-difference codes [7,8,9,10,11,12] These studies report the impact of kinetic effects in various aspects of parallel transport, including the modification of the parallel heat flux and atomic rates [9], as well as effects on the properties of the plasma sheath. Our goal in this study is tackling the comparison between a fluid and kinetic model of parallel electron transport, with a focus on extracting kinetic effects For this purpose, we avoid very (machine-)specific scenarios popular in the literature, and instead vary the input power into the SOL while keeping other parameters (such as total density) fixed. We close by summarising the electron transport model used, noting its limitations and considered extensions, and discussing the results obtained in this study
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