2D implementation of Kinetic-diffusion Monte Carlo in Eiron
This work addresses a domain-specific problem for tokamak scrape-off layer simulations by providing an incremental improvement to computational efficiency.
The paper tackles the computational bottleneck of particle-based kinetic Monte Carlo simulations in high-collisional regimes by extending the Kinetic-diffusion Monte Carlo scheme to two dimensions and implementing it in the Eiron code, resulting in a significant speedup over kinetic simulations.
Particle-based kinetic Monte Carlo simulations of neutral particles is one of the major computational bottlenecks in tokamak scrape-off layer simulations. This computational cost comes from the need to resolve individual collision events in high-collisional regimes. However, in such regimes, one can approximate the high-collisional kinetic dynamics with computationally cheaper diffusion. Asymptotic-preserving schemes make use of this limit to perform simulations in these regimes, without a blow-up in computational cost as incurred by standard kinetic approaches. One such scheme is Kinetic-diffusion Monte Carlo. In this paper, we present a first extension of this scheme to the two-dimensional setting and its implementation in the Eiron particle code. We then demonstrate that this implementation produces a significant speedup over kinetic simulations in high-collisional cases.