Abstract
The interaction between plasma and neutrals within a tokamak dominates the behaviour of the edge plasma, especially in the divertor region. This area is not quiescent, but has significant perturbations in the density and temperature due to turbulent fluctuations. Investigating the interaction between the neutrals and plasma is important for accurately simulating and understanding processes such as detachment in tokamaks. For simplicity, yet motivated by tokamak edge plasma, we simulate a linear plasma device and compare the sources and sinks due to ionisation, recombination, and charge exchange for cases with and without turbulence. Interestingly, the turbulence systematically strengthens the interaction, creating stronger sources and sinks for the plasma and neutrals. Not only does the strength of the interactions increase, but the location of these processes also changes. The recombination and charge exchange have relatively short mean free paths, so these processes occur on the scale of the eddy fluctuations, while the ionisation is mostly unaffected by the turbulence.
Highlights
In tokamaks heat is exhausted from the core into the edge plasma where it is conducted along the magnetic field onto a very thin region on the divertor plates
In addition to heat flux, particle flux through elastic collisions of molecules on the walls and divertor plays an important role in divertor conditions [2]; only particle flux is included here, and molecular flux is considered as potential future work
To decrease the heat flux, the plasma can be forced into a detached regime where much of the thermal and kinetic energy is radiated from the edge plasma and spread volumetrically
Summary
In tokamaks heat is exhausted from the core into the edge plasma where it is conducted along the magnetic field onto a very thin region on the divertor plates. To decrease the heat flux, the plasma can be forced into a detached regime where much of the thermal and kinetic energy is radiated from the edge plasma and spread volumetrically This occurs when the relatively low temperature plasma in the edge of a tokamak interacts strongly with neutrals near the divertor through charge exchange, ionisation, and recombination [3]. These atomic processes have cross-sections that are functions of the plasma temperature, density, and neutral density meaning that turbulence, which provides fluctuations in these quantities, will have a local effect on the plasma-neutral interactions. Previous effort has been made in this area with statistically generated turbulence [4] and with two-dimensional SOL turbulence in TOKAM2D [5]; we seek to use self-consistent, 3D fluid turbulent simulations
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