Greetings,

I designed a simple pierce-like electron gun in CST Studio Suite  and I used the tracking solver to see electron emission trajectory. Usually I use Tetrahedral meshing for the simulation but one time I decided to change the meshing option to Hexahedral FIT. Surprisingly, the particle trajectory is completely different! I would like to know why this happens?

This is the regular Tetrahedral mesh,

Below is the result of Hexahedral FIT.

Another problem is that, when I use Tetrahedral mesh, I cannot see the Potential fields and electric fields. CST is considering all of them zero and not showing different colours for different voltages. But when I use Hexahedral FIT mesh, I have access to all 2D/3D results. Therefore, I was wondering what the problem is and which one is more accurate?

Comparing with IBSimu Results

Previously, I used IBSimu code to perform particle tracking in electrostatic fields and the result of particle trajectory in this code is exactly same as Tetrahedral mesh result in CST. So I was happy that I can get the same results; however, as soon as I switched to hexahedral mesh, the true result is ambiguous. Below, is the result of IBSimu code showing same trajectory as the Tetrahedral mesh.

Why am I asking this?

The objective is to have a mesh grid in front of the cathode with alternating voltage to extract bunches out of the cathode. For this matter I have to use ES-PIC solver and in this solver, objects with alternating voltage are defined via signal excitations, and CST can only perform this by Hexahedral FIT. If I change it to Tetrahedral, it gives me error. I believe the Tetrahedral is more accurate but unfortunately for ES-PIC solver I cannot use this option.

Thank you for your help.