Extract from CST PARTICLE STUDIO
Usually an electron gun is only one part of a complex device, for example a particle accelerator. The gun is used to create a collimated particle beam, so that other parts of the device have a beam of good quality.
The way this gun works is quite simple. Electrons are emitted from a cathode by a particle source based on space charge limited emission. These particles are accelerated and focused by an anode. Additional focusing is realized by a set of magnets behind the anode.
The following picture shows the structure of interest. It has been sliced open to aid visualization. Anode and cathode consist of PEC whereas the magnetic structure above the anode consists of iron and permanent magnets.
Before you start modeling the structure, let's spend a few moments discussing how to describe this structure efficiently.
At first, CST PARTICLE STUDIO allows you to define the properties of the background material. Anything you do not fill with a particular material will automatically be filled with the background material. For this structure it is sufficient to model anode, cathode, two iron discs and three permanent magnets of the electron gun. The background properties will be set to vacuum.
Your method of describing the structure should therefore be as follows:
Model cathode and anode of the electron gun.
Model the two iron discs.
Model the three permanent magnets.
Further information can be obtained from the "Workflow and Solver Overview" documentation.