Secondary electrons can be emitted from a electron species, charged particle species, or neutral particle species. They can then be emitted into a separate electron species, or into the same electron species.
To specify a secondary emitter an emitter boundary type must be chosen, as well as an emission specification algorithm.
The available types of emitter boundaries are.
boundary emitter This is any Boundary Absorb and Save boundary condition, no other specification is necessary.
cut cell emitter This is any Cut-Cell Absorb and Save boundary condition, no other specification is necessary.
interior emitter This is any Interior Absorb and Save Boundary Condition. It does require specification of a few more parameters.
- emission axis
The axial direction particles will be emitted in.
- emission direction
Either positive or negative, particles will be emitted in this direction along the emission axis.
- emission coordinate
- The precise coordinate at which the emission will occur. Effectively this is an offset from the position of the particle
boundary condition.
4 types of emission specification are available in VSim.
material properties This will emit particles according to the Furman and Pivi algorithm for either copper or stainless steel. If using variable, or managed weight particles it is also necessary to specify a minimum weight for the emitted particle.
constant probability This will emit particles with a predefined probability, between 0.0 and 1.0.
- simple
A secondary emitter that at most emits a single secondary electron macroparticle. An instance of simpleSec, follow the link for more information.
- emission probability
The probability of a particle being emitted. This is slightly different from the constant probability secondary electron emitter as this will emit only a single electron, with a prescribed probability independent of all other factors.
- emitted energy
The energy of the emitted electrons if constant weight particles are used.
Furman and Pivi This will emit electrons according to the Furman and Pivi algorithm. See table 1 of [FP02] For an example of how these are computed. Note this is only available for use with cut cull emitters.
- E0
Total energy of the secondary electron yield, must be multiplied by ELEMCHARGE.
- D_MAX
Max Delta of the secondary electron yield.
- minimum weight
Only specified if using a variable or managed weight particle species, the emitted secondary electron must be above this weight to be emitted.