Discussion Forum

Hi all,


I am new to this forum and to COMSOL for that matter. I have started using COMSOL a few weeks ago and I ran into some problems.

I have started with an easy enough problem. Two parallel plates separated by a distance and on one of the plates I have placed an emisphere. The plate with the emisphere is the cathode the other one is the anode. I have placed the whole thing in a big cylinder and used the zero charge/symmetry boundary condition. Sorry I forgot to mention this whole thing was done in 3D.

All went well and the electric potential was computed everywhere within the big cylinder surrounding the two plates. The problem I am having is with the particle tracing feature. I wanted to see what happens when I "fly" some electrons from the sphere. I can do that is I try to figure out some of the points on the sphere but this is quite a difficult task to do for more complicated geometries. In the help file it is stated that the particle tracing in 3D is the same as the one in 2D but I find there are completely different settings for the two.

For example, in the 2D case there is an option to specify the boundary coordinates where you want your particles to fly from which is a useful feature although is not working very well (or I don't know how to make it work, any help is appreciated). In the 3D case this feature does not exist. There is no way to specify a certain boundary where particles can fly from. You have to do it manually using the (x,y,z) coordinate. This could be fun for someone but I find is a bit impractical (again if I am missing something please point me in the right direction).

Is there a way I can specify a region on my geometry (be it in 3D or 2D) where I can tell COMSOL to show me the paths of a number of particles (electrons) flying from that region?

I appreciate any kind of help and if you want to see better the example I was tried these features on I can attach it to a later post.


Cheers,

Lucian