# Electromagnetic Particle In Cell (emPtclInCellT.pre)

Keywords:

electromagnetics, particle in cell, sheath, box bounding

## Problem description

A point antenna launches a wave from a point that is midway in x and z (if two-dimensional) but 1/3 of the way up from the bottom in y. The electromagnetic field and plasma respond self consistently to an antenna current, if set, or else the plasma simply evolves due to its initial thermal distribution.

This simulation can be performed with a VSimBase license.

## Opening the Simulation

The Electromagnetic Particle In Cell example is accessed from within VSimComposer by the following actions:

• In the resulting Examples window expand the VSim for Basic Physics option.
• Expand the Basic Examples (text-based setup) option.
• Select “Electromagnetic Particle In Cell” and press the Choose button.
• In the resulting dialog, create a New Folder if desired, and press the Save button to create a copy of this example.

The key parameters of this problem should now be alterable via the text boxes in the left pane of the Setup Window, as shown in Fig. 151.

Fig. 151 Setup Window for Electromagnetic Particle in Cell.

## Input File Features

The input file sets the number of cells along each direction along with the lengths of each direction. The transverse (y, z) boundary conditions are periodic. There are slab conductors at the limits in x.

The number of vacuum wavelengths in the box can be chosen. The wave frequency $$\omega$$, is then given from the vacuum dispersion relation $$\omega = c/\lambda$$.

Particles are loaded on a grid with a thermal velocity to generate a plasma with plasma frequency equal to OMP_REL times the wave frequency. For the wave amplitude, the antenna strength should satisfy DEZ_ANT > 1.e9*OMP_REL^2.

The time step is chosen to be TIMESTEP_FACTOR times the combined stability limit for plasma oscillations and that given by the CFL limit for FDTD electromagnetics.

One can turn the antenna off to see just the plasma noise and sheath generation.

## Running the Simulation

After performing the above actions, continue as follows:

• Proceed to the Run Window by pressing the Run button in the left column of buttons.
• To run the file, click on the Run button in the upper left corner. of the window. You will see the output of the run in the right pane. The run has completed when you see the output, “Engine completed successfully.” This is shown in Fig. 152.

Fig. 152 The Run Window at the end of execution of Electromagnetic Particle in Cell.

## Visualizing the Results

After performing the above actions, continue as follows:

• Proceed to the Visualize Window by pressing the Visualize button in the left column of buttons.

To view the electric field, expand “Scalar Data”, expand the E field box, and select E_magnitude. Move the slider at the bottom of the right pane to see the electric field at different times. At Dump 4, the rings of radiation surrounding the antenna can be seen, as shown in Fig. 153. box, as shown below.

## Further Experiments

Vary the antenna amplitude, DEZ_ANT, to find out how low it can be before the signal is swamped by the plasma noise.

Increase OMP_REL to 1.5 to see that a wave is no longer launched, but what causes that front that travels far from the antenna.

Add in a magnetic field in the plane; remove the magnetic field out of the plane. Launch a mode with frequency above the upper-hybrid. Does the shape of the fronts change?