SPARK3D User Manual
Setting a Corona configuration

Adding a new Corona configuration

It is possible to create as many Corona configurations as needed in the Corona Configuration Group. This way, you can analyze Corona discharge in the same device with different Corona parameters. For example, you can change the type of gas (dry air or nitrogen).

In order to create a new Corona configuration, right-click on the Corona Configuration Group tree item and select Add Corona Configuration option as is shown below

A new Corona configuration item will appear in the tree in the framework of the Corona Configuration Group.

Setting Corona configuration parameters

Corona configuration parameters are set from its corresponding window, which can be opened from the Corona configuration tree item by double clicking on it or using Open Corona Configuration right-click option.

Corona configuration window

It looks like this:

The meaning of the different parameters is the following:


Through this option the user can choose the specific regions of the structure where the analysis will be carried out by simply enabling their check-boxes. If a region, that has been previously simulated, is disabled, its results will be preserved and shown in Corona configuration results window. This way, the user can incorporate new regions of analysis keeping the results of the already defined ones. 

It is also possible to access the Analysis Regions window from the Edit Regions button. It is important to point out that all modifications made on the regions from that window will apply to all configurations. So, if a region, which is used in several configurations both of Corona and Multipactor, is changed or deleted all existing results corresponding to it will be erased.

Minimum pressure (mBar) Pressure at which the pressure sweep will start.
Maximum pressure (mBar) Pressure at which the pressure sweep will finish.
Pressure step(mBar) Step in pressure for the pressure sweep.
Gas Two gases can be considered in the simulation: nitrogen and dry air. Nitrogen will always provide a lower corona breakdown power level.
Temperature (K) Ambient Temperature. The reference is taken as the room temperature of 293 K.
Simulation type Three different simulation types can be considered:
  • Numerical, which corresponds to a numeric algorithm that uses an adapted FEM technique to solve the free electron density continuity equation.
  • Analytical rule, which is detailed in high pressure analytical rule section.
  • Numerical & analytical, which enables both simulation types.
Initial power (W)

Power from which the threshold breakdown power is looked for. It must be set only for "Numerical" and "Numerical & analytical" simulation types. Its value may be set by the user or it may be taken automatically (enabling the "Automatic" check box) from the high pressure analytical approach.

Precision (dB) This parameter sets the desired precision in power level for the corona breakdown onset.

Any modification in the above parameters can be confirmed with the OK button and will lead to deleting all existing results. Otherwise, the user can also cancel this action through Cancel button.

There is only one exception to this behavior: the selection of regions. If one region which was already simulated is disabled for analysis, its results are kept and shown in results window.

High pressure analytical rule

At high pressures, where diffusion is negligible, it is also possible to include the breakdown power threshold corresponding to a high pressure analytical rule by selecting in Simulation Type parameter of Corona configuration either the option "Conservative (Analytical)" or "Numerical & Analytical" . 

The obtained results are based on the well-known relation for ionization breakdown at sea level (W. Woo and J. DeGroot, Microwave absorption and plasma heating due to microwave breakdown in the atmosphere", IEEE Physical Fluids, vol. 27, no. 2, pp. 475-487, 1984), which in the case of air corresponds to:

Ebreakdown = 30.17 (pressure^2 + 2·frequency^2)^0.5 (V/cm)

This rule is conservative at all pressure ranges. At high pressures, it gives an estimation for the breakdown power threshold whereas at low pressures - where diffusion losses are much more important- this rule only results in a very conservative breakdown onset.

It is important to point out that the results are extremely dependent on the maximum value of the Electric field magnitude, Emax. This means that if this value changes, the high pressure analytical results will also change. Such a modification usually occurs in problems where the maximum electric field is concentrated on small localized regions, like in devices where metal corners are present. There are several reasons for such a variation: