How to Track particles with some initial conditions?

[Changxiang-Mao]

Hi,

I am running 2D PIC simulations, with Lx =128, Ly = 16. I want to track those macro-particles that locate within 10<x<11, 5<y<6 initially. So I add the module:

def my_filter(P):
    return (P.x>10)*(P.x<11)*(P.y>5)*(P.y<6)

DiagTrackParticles(
    species = "eon",
    every = every,
    flush_every = every * 5,
    filter = my_filter,
    attributes = ["x", "y"],
)

The whole script is

a0.py

However, when I use diag = S.TrackParticles("eon", axes = ["x","y"]).getData(), it shows there are 1093 particles contained. From the parameters, dx = dy = 0.25, Nppc = 4, so the region 10<x<11, 5<y<6 contains just 64 particles.

I wonder why this happens? And what should I do to track those particles that locate in 10<x<11,5<y<6 initially?

[mccoys]

Hi

Please use discussions for this kind of question (this was transferred to discussions)

[mccoys]

In the namelist, the filter = my_filter parameter carries out this filter every time particles are written to the disk. They may not be the same particles every time.

If you want to track particles that have initially some condition you must recall something from the documentation (https://smileipic.github.io/Smilei/Use/namelist.html#filter):

The id attribute contains the particles identification number. This number is set to 0 at the beginning of the simulation. Only after particles have passed the filter, they acquire a positive id.

This means that you can make a different filter initially, and use the fact that id > 0 only for those which have passed the filter at t=0/

def my_filter(P):
    if Main.iteration == 0:
        return (P.x>10)*(P.x<11)*(P.y>5)*(P.y<6)
    else:
        return P.id > 0

[Changxiang-Mao]

I understand. Thank you.