April 4-6

Abstract Details

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Author: George J. Wilkie
Requested Type: Consider for Invited
Submitted: 2022-03-04 14:04:11


Contact Info:
Princeton Plasma Physics Laboratory
PO Box 451
Princeton, NJ   08543

Abstract Text:
In high-recycling and detached regimes, the details of neutral transport and collisions become increasingly important in determining the edge plasma performance and degradation of plasma-facing components. Monte Carlo methods are a robust and efficient method of estimating neutral transport properties and their interaction with a fixed plasma background. However, the stochastic error from noise, despite ostensibly limited to acceptable levels, interferes when iterating with deterministic models for the plasma. Furthermore, collision processes which are important for cold divertors become exceedingly expensive for Monte Carlo methods since this involves solving the full nonlinear Boltzmann equation. For this reason, a nonlinear BGK model is typically used in kinetic neutral simulations to handle processes such as elastic scattering between neutrals and charge exchange with non-Maxwellian ions. A conservative spectral nonlinear Boltzmann solver, LightningBoltz, has been recently developed to rigorously treat such processes. Among other benchmarks, detailed comparison between LightningBoltz and DEGAS2 will be presented, highlighting the differences between the current BGK model and the Boltzmann operator for nonlinear elastic scattering. In addition, a fully kinetic treatment of charge exchange is presented which is being implemented for coupled XGC-DEGAS2 simulations. These techniques will enable rigorous simulation of neutrals in advanced divertor environments to predict their ability to cool the plasma while maintaining favorable edge plasma conditions.

1. Computer Simulation of Plasmas.
2. Physics of Plasma Edge and Divertor Region.