Kinetic simulations of collisionless plasmas in open magnetic geometries
Abstract
Laboratory plasmas in open magnetic geometries can be found in many different applications such as (1) ScrapeOfLayer (SOL) and divertor regions in toroidal confinement fusion devices (\approx110^2\hspace{1mm}\mathrm{eV}), (2) linear divertor simulators (\approx110\hspace{1mm}\mathrm{eV}), (3) plasmabased thrusters (\approx10\hspace{1mm}\mathrm{eV}) and (4) magnetic mirrors (\approx10^210^3\hspace{1mm}\mathrm{eV}). A common feature of these plasma systems is the need to resolve, in addition to velocity space, at least one physical dimension (e.g. along flux lines) to capture the relevant physics. In general, this requires a kinetic treatment. Fully kinetic ParticleInCell (PIC) simulations can be applied but at the expense of large computational effort. A common way to resolve this is to use a hybrid approach: kinetic ions and fluid electrons. In the present work, the development of a hybrid PIC computational tool suitable for open magnetic geometries is described which includes (1) the effect of nonuniform magnetic fields, (2) finite fullyabsorbing boundaries for the particles and (3) volumetric particle sources. Analytical expressions for the momentum transport in the paraxial limit are presented with their underlying assumptions and are used to validate the results from the PIC simulations. The selfconsistent electric field is calculated and is shown to modify the ion velocity distribution function in manner consistent with analytic theory. Based on this analysis, the ion distribution function is understood in terms of a losscone distribution and an isotropic MaxwellBoltzmann distribution driven by a volumetric plasma source. Finally, inclusion of a MonteCarlo based FokkerPlanck collision operator is discussed in the context of future work.
 Publication:

arXiv eprints
 Pub Date:
 June 2021
 arXiv:
 arXiv:2106.01201
 Bibcode:
 2021arXiv210601201K
 Keywords:

 Physics  Plasma Physics
 EPrint:
 This a paper on Hybrid PIC simulations of plasmas in open magnetic geometries