unexpected density decrease with particle injector

[rl3418]

injection.txt
I modified the example script for 2D particle injection. So I defined the species to have a constant density beyond a certain distance and injected the particles from xmax. It is working well with 'random' position intialisation, but when I switch to 'regular', the injected particles are at a slightly lower density than the specified value as shown in the figure attached.

[xxirii]

Hi @rl3418,

This problem is known and partially explained in https://smileipic.github.io/Smilei/Understand/particle_injector.html
I made some tests this morning just to be sure you were not observing a new problem.

Some particles do not cross the boundary during the timestep dt leading to lower density. The phenomenon will be less visible if you use more particles. The problem comes from the way we inject particles. We have some ideas to fix that but not yet implemented. This is not a bug but a model issue.

I suggest you use the random distribution with the injector.

[rl3418]

Thanks for your reply. I will try that then. When I initialise the injected species, is it possible for it to only have non-zero density beyond the simulation box? Though the density will be lower, I guess that will give the particles the same density at least.