Settable Slab Flux Emitter
All particle types may emit from a slab settable flux emitter. Certain emission specifications are only available based on particle type and particle weights specification. Available in all coordinate simulations.
start time Time to start emitting particles in seconds.
stop time Time to stop emitting particles in seconds.
- emission specification: Specification of the emitted
particles, note that the specification options vary for constant or variable/managed weight particles.
emission current density
emission current density: Specify the current density of the emitter (amps/meter^2). Can be a spatial profile.
velocity coordinate system: Either global or surface. A global coordinate system will specify the emission velocities according to global axis. A surface coordinate system will set the emission directions according to the normal of the emission object. So in a surface coordinate system a lower simulation bounds the emission velocity must be negative to emit into the simulation space, for an upper simulation boundary the particles must be positive to emit into the simulation space.
mean velocity 0: The average (mean) speed of particles in the x-direction when velocity coordinate system is set to “global”. If set to “surface” then this will be the average velocity for the direction normal to the emitting surface.
mean velocity 1: The average (mean) speed of particles in the y-direction when velocity coordinate system is set to “global”. If set to “surface” then this will be the average velocity for a direction perpendicular to the emitting surface.
mean velocity 2: The average (mean) speed of particles in the z-direction when velocity coordinate system is set to “global”. If set to “surface” then this will be the average velocity for a direction perpendicular to the emitting surface.
thermal velocity 0: A spread (standard deviation) for particle speeds in the 0 direction.
thermal velocity 1: A spread (standard deviation) for particle speeds in the 1 direction.
thermal velocity 2: A spread (standard deviation) for particle speeds in the 2 direction.
emission flux
emission flux Specify the flux of the emitter (particles/meter^2). Can be a spatial profile.
velocity coordinate system: Either global or surface. A global coordinate system will specify the emission velocities according to global axis. A surface coordinate system will set the emission directions according to the normal of the emission object. So in a surface coordinate system a lower simulation bounds the emission velocity must be negative to emit into the simulation space, for an upper simulation boundary the particles must be positive to emit into the simulation space.
mean velocity 0: The average (mean) speed of particles in the x-direction when velocity coordinate system is set to “global”. If set to “surface” then this will be the average velocity for the direction normal to the emitting surface.
mean velocity 1: The average (mean) speed of particles in the y-direction when velocity coordinate system is set to “global”. If set to “surface” then this will be the average velocity for a direction perpendicular to the emitting surface.
mean velocity 2: The average (mean) speed of particles in the z-direction when velocity coordinate system is set to “global”. If set to “surface” then this will be the average velocity for a direction perpendicular to the emitting surface.
thermal velocity 0: A spread (standard deviation) for particle speeds in the 0 direction.
thermal velocity 1: A spread (standard deviation) for particle speeds in the 1 direction.
thermal velocity 2: A spread (standard deviation) for particle speeds in the 2 direction.
emission current
emission current Specify the total emitted current per second from the emitter (amps/second).
profile Spacetime function that multiplies the total emission current per second.
velocity coordinate system: Either global or surface. A global coordinate system will specify the emission velocities according to global axis. A surface coordinate system will set the emission directions according to the normal of the emission object. So in a surface coordinate system a lower simulation bounds the emission velocity must be negative to emit into the simulation space, for an upper simulation boundary the particles must be positive to emit into the simulation space.
mean velocity 0: The average (mean) speed of particles in the x-direction when velocity coordinate system is set to “global”. If set to “surface” then this will be the average velocity for the direction normal to the emitting surface.
mean velocity 1: The average (mean) speed of particles in the y-direction when velocity coordinate system is set to “global”. If set to “surface” then this will be the average velocity for a direction perpendicular to the emitting surface.
mean velocity 2: The average (mean) speed of particles in the z-direction when velocity coordinate system is set to “global”. If set to “surface” then this will be the average velocity for a direction perpendicular to the emitting surface.
thermal velocity 0: A spread (standard deviation) for particle speeds in the 0 direction.
thermal velocity 1: A spread (standard deviation) for particle speeds in the 1 direction.
thermal velocity 2: A spread (standard deviation) for particle speeds in the 2 direction.
emission rate
emission rate Specify the total number of particles emitted per second (particles/second)
profile Spacetime function that multiplies the total emission current per second.
velocity coordinate system: Either global or surface. A global coordinate system will specify the emission velocities according to global axis. A surface coordinate system will set the emission directions according to the normal of the emission object. So in a surface coordinate system a lower simulation bounds the emission velocity must be negative to emit into the simulation space, for an upper simulation boundary the particles must be positive to emit into the simulation space.
mean velocity 0: The average (mean) speed of particles in the x-direction when velocity coordinate system is set to “global”. If set to “surface” then this will be the average velocity for the direction normal to the emitting surface.
mean velocity 1: The average (mean) speed of particles in the y-direction when velocity coordinate system is set to “global”. If set to “surface” then this will be the average velocity for a direction perpendicular to the emitting surface.
mean velocity 2: The average (mean) speed of particles in the z-direction when velocity coordinate system is set to “global”. If set to “surface” then this will be the average velocity for a direction perpendicular to the emitting surface.
thermal velocity 0: A spread (standard deviation) for particle speeds in the 0 direction.
thermal velocity 1: A spread (standard deviation) for particle speeds in the 1 direction.
thermal velocity 2: A spread (standard deviation) for particle speeds in the 2 direction.
- Fowler Nordheim Emission:
Specify particle emission according to the Fowler-Nordheim model. Only available with variable or managed weight electron particle species that are not speed-limited.
work function [eV]: Work function of the material from which emission is occurring.
A: Coefficient A of the Fowler-Nordheim emission model.
B: Coefficient B of the Fowler-Nordheim emission model.
field enhancement: Multiplies the measured electric field by this amount.
Cv: Coefficient Cv of the Fowler-Nordheim emission model.
Cy: Coefficient Cy of the Fowler-Nordheim emission model
- Richardson Dushman Emission:
Specify particle emission according to the Richardson-Dushman model. Only available with variable or managed weight electron particle species that are not speed-limited.
work function [eV]: Work function of the material from which emission is occurring. Parameter in the Richardson-Dushman model.
field evaluation offset:
temperature (K): Temperature of the material from which emission is occurring. Parameter in the Richardson-Dushman model.
field enhancement: Multiplies the measured electric field by this amount.
flux multiplier: Multiplies the resulting output current by this amount.
- Child Langmuir Emission:
Specify particle emission according to the Child Langmuir model. Only available in simulations with variable or managed weight electron particle species that are not speed-limited.
- space charge limited emission:
This will limit the current to provide a more consistent emission current, providing higher accuracy particularly in explosive emission cases, such as a pulsed power magnetron. For non pulsed-power simulations it is not necessary.
mean velocity 0: The average (mean) speed of particles in the 0 direction.
mean velocity 1: The average (mean) speed of particles in the 1 direction.
mean velocity 2: The average (mean) speed of particles in the 2 direction.
thermal velocity 0: A spread (standard deviation) for particle speeds in the 0 direction.
thermal velocity 1: A spread (standard deviation) for particle speeds in the 1 direction.
thermal velocity 2: A spread (standard deviation) for particle speeds in the 2 direction.
emission offset The distance away from the object that emitted particles are placed, as a fraction of a cell length in the signed normal direction from the emitter slab. This is useful when absorbing and emitting the same particle species from a given location.
physical offset The distance away from the object that emitted particles are placed, in meters, in the signed normal direction from the emitter slab. This is used when one wants to place the emission of particles farther away from the emission face than a fraction of a cell. Physical offset and emission offset add to give the total offset. For instance, if the emission surface normal is in the X-direction, then the total offset is calculated as \(\delta_t = \delta_e \Delta_X + \delta_p\), where \(\delta_e\) is the emission offset, \(\Delta_X\) is the cell size in the X-direction, \(\delta_p\) is the physical offset.
NOTE: To allow the user to emit from non-Maxwellian probability distribution functions, one can import a Python space time function (see the “SpaceTimeFunctions” section in the Reference manual). The easiest way to do this is to right-click with your mouse on the component of the mean velocity you wish to emit (for example mean velocity 0) then click on Assign SpaceTimeFunction and finally choose the python SpaceTimeFunction you have already defined. It is best not to mix this method with the default method of choosing the velocity from a Maxwellian. Therefore, when you write your python SpaceTimeFunction, include all drift- and thermal-velocity terms in the Python function. Then leave the thermal velocity 0 option set to 0.0. Also, all three components are independent. So if your python function depends only on component 0, then you could treat the other two components as Maxwellian and fill in the mean velocity and thermal velocity options using the methods discussed above for components 1 and 2.