Space Charge Density Calculation
Use the Space Charge Density Calculation node if space charge effects are important. This node defines a dependent variable for the space charge density in the selected domains. Optionally, the current density can also be computed.
The Space Charge Density Calculation node computes space charge density and current density in the same way as the Electric Particle Field Interaction and Magnetic Particle–Field Interaction Multiphysics nodes, respectively, but does not automatically include the accumulated variables as source terms when computing the fields. For modeling bidirectionally coupled particle-field interactions, consider using The Particle–Field Interaction, Nonrelativistic Interface or The Particle–Field Interaction, Relativistic Interface instead of the Space Charge Density Calculation node.
For more information about the calculation of the space charge density, see Space Charge Density Calculation in the section Theory for the Particle–Field Interaction, Nonrelativistic Interface. For more information about the calculation of current density, see Current Density Calculation in the section Theory for the Magnetic Particle–Field Interaction, Relativistic Interface.
Space Charge Density Calculation
If Specify release times is selected from the Particle release specification list in the physics interface Particle Release and Propagation section, enter a value or expression for the Charge multiplication factor n (dimensionless). The default is 106. The Charge multiplication factor can be used to represent each particle as a group of n particles that follow the same trajectory. This means that the magnitude of the contribution to the space charge density by each particle is multiplied by n. It is thus possible to model space charge effects without allocating degrees of freedom for an overwhelming number of particles.
If Specify current is selected from the Particle release specification list in the physics interface Particle Release and Propagation section, the Charge multiplication factor n cannot be specified because the number of charged particles represented by each model particle is instead controlled by the Release current magnitude, which is specified in the settings for release features such as theRelease and Inlet nodes.
Select the Compute current density check box to allocate additional degrees of freedom for the components of the current density.
The following features are specific applications of the core functionality used in the Accumulator (Boundary) subnode, described in The Mathematical Particle Tracing Interface.