The Particle–Field Interaction, Nonrelativistic Interface
The Particle–Field Interaction, Nonrelativistic () multiphysics interface combines the Charged Particle Tracing interface with the Electrostatics interface. The Electric Particle Field Interaction multiphysics coupling feature is added automatically. The Particle–Field Interaction, Nonrelativistic interface is used to model beams of charged particles at nonrelativistic speeds. The particles generate a space charge density term as they propagate through domains. The space charge density is then used as a source term in the Electrostatics interface, and the resulting electric force on the particles is computed.
When a predefined Particle–Field Interaction, Nonrelativistic interface is added from the AC/DC>Particle Tracing branch () of the Model Wizard or Add Physics windows, Electrostatics and Charged Particle Tracing interfaces are added to the Model Builder. A Multiphysics Couplings node is also added, which automatically includes the Electric Particle Field Interaction multiphysics coupling.
On the Constituent Physics Interfaces
The Electrostatics interface is used to compute the electric field, the electric displacement field and potential distributions in dielectrics under conditions where the electric charge distribution is explicitly prescribed. The formulation is stationary but for use together with other physics, also eigenfrequency, frequency-domain, small-signal analysis, and time-domain modeling are supported in all space dimensions. The physics interface solves Gauss’ law for the electric field using the scalar electric potential as the dependent variable.
The Charged Particle Tracing interface is used to model charged particle orbits under the influence of electromagnetic forces. In addition, it can also model bidirectional coupling between the particles and fields. Some typical applications are particle accelerators, vacuum tubes, and ion implanters. The physics interface supports time-domain modeling only in 2D and 3D. The physics interface solves the equation of motion for charged particles subjected to electromagnetic forces.
Settings for Physics Interfaces and Coupling Features
When physics interfaces are added using the predefined couplings — for example, Particle–Field Interaction, Nonrelativistic — specific settings are included with the physics interfaces and the coupling features. However, if physics interfaces are added one at a time, followed by the coupling features, these modified settings are not automatically included.
For example, if single Electrostatics and Charged Particle Tracing interfaces are added, an empty Multiphysics Couplings node appears. You can choose from the available coupling features but the modified settings are not included.
Coupling features are available from the context menu (right-click the Multiphysics Couplings node) or from the Physics toolbar, Multiphysics menu.
Table 6-1: Modified Settings for a Particle Field Interaction, Nonrelativistic Interface.
Physics Interface or Coupling Feature
Modified Settings (if any)
Electrostatics
No changes.
Charged Particle Tracing
For the Charged Particle Tracing interface, under Particle Release and Propagation, the Particle release specification is set to Specify current.
The Electric Force node is added to the Charged Particle Tracing interface. The Domain Selection is the same as that of the Charged Particle Tracing interface.
Electric Particle Field Interaction
The Domain Selection is the same as that of the participating physics interfaces.
The corresponding Electrostatics and Charged Particle Tracing interfaces are preselected in the Electric Particle Field Interaction section.
Physics Interfaces and Coupling Features
Use the online help in COMSOL Multiphysics to locate and search all the documentation. All these links also work directly in COMSOL Multiphysics when using the Help system.
Coupling Features
The Electric Particle Field Interaction and Space Charge Limited Emission coupling feature nodes are described in this section.
Physics Interface Features
Physics nodes are available from the Physics ribbon toolbar (Windows users), Physics context menu (Mac or Linux users), or right-click to access the context menu (all users).
In general, to add a node, go to the Physics toolbar, no matter what operating system you are using. Subnodes are available by clicking the parent node and selecting it from the Attributes menu.
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The available physics features for The Charged Particle Tracing Interface are listed in the section Domain, Boundary, Pair, and Global Nodes for the Particle Tracing for Fluid Flow Interface.
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The available physics features for The Electromagnetics Interfaces are listed in the section Domain, Boundary, Edge, Point, and Pair Nodes for the Electrostatics Interface in the COMSOL Multiphysics Reference Manual.