Progress in Kinetic Simulation of Edge Plasmas

Abstract

Kinetic codes are required for quantitative simulation of edge plasmas of most tokamaks, because orbit widths can be comparable to radial scale lengths and because mean free paths can be comparable to scale lengths along the magnetic field. However, the edge presents special challenges for edge simulation, both in terms of formulation and implementation. There are two major approaches to kinetic simulation, namely particle-based and continuum-(high-dimensional fluid-) based. The edge presents challenges common to both approaches as well as ones that are unique to each approach. In this paper we review these challenges, and survey how they are being addressed in current edge kinetic simulation projects, as well as the status and accomplishments of those projects. We discuss in some detail the status and recent accomplishments of the U.S. Edge Simulation Laboratory (ESL), a project based on the continuum approach. The ESL currently consists of a main-line effort to develop a code based on high-order conservative finite-volume discretization, as well as two prototype activities, TEMPEST and EGK. These prototype codes are exploring issues attached to energy-magnetic moment and parallel velocity-magnetic moment representations, respectively, as well as physics issues associated with simulation in a steep radial gradient region and a domain that includes both open field lines and closed flux surfaces.

Modeling and Simulation on SOL-Divertor Plasmas

“…the particle modeling for edge plasma simulations is very easier to set the boundary condition, and is very flexible to introduce the A&M processes [16][17][18][19].…”

“…The flow is expected to expel Helium ashes and to retain impurities enhancing the radiative cooling in the divertor region, if the flow is directed towards the divertor plate. Kinetic simulations are considered to bring a breakthrough on this subject [19,22,43]. This backward flow is seen when the single null point is located in the ion ∇B drift direction, while it vanishes for the reversed null-point location [30][31][32].…”

Modelling of Ion Kinetic Effects for SOL Flow Formation

“…Kinetic simulations are considered to bring a breakthrough on this subject [13][14][15]. Kinetic models are able to simulate the effects of drifts, finite-size orbit, self-consistent electric fields including sheath etc., which are considered to play important roles in the SOL flow formation.…”

On Recent Massively Parallelized PIC Simulations of the SOL

“…see [12]), and are massively parallel [13]. Brief descriptions of different kinetic models of the SOL can be found in [14,15]. Here we mention just the main achievements in these studies.…”