Physics Features of VORPAL

Kinetic Plasma Model and Direct Simulation Monte-Carlo (DSMC) algorithm

The kinetic plasma model incorporated in VORPAL is based on the particle-in-cell (PIC) algorithm both in the electromagnetic and electrostatic limit. In the electromagnetic case, a charge conserving current deposition algorithm enables the integration of Maxwell's equations without any additional divergence cleaning. In the electrostatic limit, Poisson's equation is solved at every timestep based on the instantaneous charge distribution. The plasma can be confined in arbitrary shaped structures for particles and fields, including conductors, particle absorbers, reflectors, and many more. The computational domain can be periodic or mimic infinity via perfectly matched layer boundary conditions.

VORPAL offers models for neutral gases, both as neutral fluids or as kinetic gases. The kinetic gas model is based on the Direct Simulation Monte-Carlo (DSMC) algorithm. Particle emission models include photo cathodes, field induced emitters, and space-charge limited emitters.

Ionization

VORPAL offers models for neutral gases, both as neutral fluids or as kinetic gases. Ionization models are provided through the TxPhysics library, also developed by Tech-X Corporation. Field ionization is based on the ADK ionization model, whereas the impact ionization model is based on parameterized cross sections discussed in Theory and Design of Charged Particle Beams. Particle emission models include photo cathodes, field-induced emitters, space-charge limited emitters, and secondary emission processes.

Secondary Emission

The Tech-X library TxPhysics is built into VORPAL, allowing simulation of phenonoma such as the electron cloud effect and grazing-incidence collisions. With this secondary emission capibility, VORPAL can create accurate numerical models of grazing-incidence collisions between ions and walls, allowing heavy-ion fusion codes and similar models determine ways to mitigate or take advantage of secondary electron emission.