What Can the Particle Tracing Module Do?

The Particle Tracing Module is a general purpose, flexible tool that is used to compute the trajectories of particles. The particles can be affected by various forces, particle-boundary interactions, and particle-domain interactions. Unidirectional and bidirectional couplings between particles and external fields are also supported.

A custom physics interface is available for modeling the motion of electrons and ions in electromagnetic fields. This makes it possible to model devices such as magnetic lenses, electron guns, and mass spectrometers. There are a number of tools available to extract typical quantities of interest and to make plots of the particle trajectories, including phase portraits and Poincaré maps. Built-in multiphysics interfaces are available to model the interaction of particles with electric and magnetic fields. Dedicated features are available to perform Monte Carlo simulations of the collisions between ions or electrons and the molecules in a rarefied gas.

There is also a dedicated physics interface for computing particle trajectories in a fluid system. There is a wide variety of predefined forces, including drag, gravity, electric, and Brownian forces. Fluid-based particle tracing allows for detailed investigation of mixing, separation, and filtering devices. Furthermore, built-in features are available for modeling complicated physical processes such as thermophoresis, dielectrophoresis, magnetophoresis, and acoustophoresis.

A mathematical particle tracing interface provides complete freedom and flexibility to define the equations of motion governing particle trajectories. In addition to built-in models to describe Newton’s law of motion, there are dedicated formulations available to specify the Lagrangian or Hamiltonian that dictates the motion of the particles.

All of the physics interfaces provide many different ways of releasing particles. Particles can be released from geometric entities of any level, including domains, boundaries, edges, and points. They can also be released by specifying the initial coordinates directly or by importing sets of initial coordinates from a file. Particles can also be released at multiple different times. There are many options available for describing how the particles interact with boundaries, including diffuse and specular reflection, sticking probabilities, and secondary particle emission.

The physics interfaces can all be used with COMSOL Multiphysics, but when tracing charged particles the AC/DC Module is often beneficial because it can be used to model complex alternating or direct current systems and includes more options for computing magnetic fields. If the particles move through a rarefied gas, as is often the case for ion and electron beams in vacuum systems, the Molecular Flow Module is useful because it provides built-in tools to compute the density of extremely rarefied gases. Similarly, when tracing particles in a fluid system the CFD Module or Microfluidics Module is often useful due to the multitude of advanced fluid flow features available in those modules.