Zainab,
For electrons, the Insulation boundary condition specifies zero normal electron flux at the boundary. For ions, zero normal flux is specified simply by not applying any surface reaction at a boundary that is external to the plasma. The flux consists of the sum of the migrative and diffusive fluxes, so a zero flux boundary condition does not necessarily specify zero gradient in electron/ion density normal to the boundary.
To specify a zero gradient, the no flux boundary condition needs to be combined with a specification of zero normal electric field (e.g. the Zero Charge boundary condition). The default boundary conditions for external boundaries (Zero Charge, Insulation, no surface reactions) combine to set a zero normal gradient for electron and ion densities.
--
Luke Gritter
AltaSim Technologies
For electrons, the Insulation boundary condition specifies zero normal electron flux at the boundary. For ions, zero normal flux is specified simply by not applying any surface reaction at a boundary that is external to the plasma. The flux consists of the sum of the migrative and diffusive fluxes, so a zero flux boundary condition does not necessarily specify zero gradient in electron/ion density normal to the boundary.
To specify a zero gradient, the no flux boundary condition needs to be combined with a specification of zero normal electric field (e.g. the Zero Charge boundary condition). The default boundary conditions for external boundaries (Zero Charge, Insulation, no surface reactions) combine to set a zero normal gradient for electron and ion densities.
--
Luke Gritter
AltaSim Technologies
