I want to simulate the projection of the spatial distribution of the photon beam after it passes through some object, so I want to score the current on a plane behind the module. The current score of the usrbdx seems to only have 1D statistics, but I want a 2D projection of the number of photons passing through the plane. Although the usrbin card can get 2D projection data, it does not seem to have a current scoring function.
Is there any other way to get the data I want?
Thank you!

Indeed, there is no 2D current related estimator in USRBIN. There is fluence instead, as more meaningful in terms of physics. If you want to just see (display) the 2D spatial distribution you could use USRBIN fluence scoring and apply it to a ‘thin’ surface at your location of interest.

Dear Elzbieta，
Thank you for your advice.
Yes, I’ve already tried what you’re talking about, I’ve used usrbin to score fluence for a very thin bin,and I got some results.But according to the flux calculation algorithm, we can get this equation, which looks like this:

so，I can make the surface very thin, but the fluence is always weighted by the Angle at which the photon enters the plane.
In theory, no matter how thin the surface, the actual current(number of particles) is always less than the fluence for my case(because of the scatter).
I don’t know if my understanding is correct,because I want a 2D spatial distribution of the number of photons passing through the surface.
If there is something wrong with my analysis, can you help me correct it.
thank you!
chen

You are absolutely right with the fluence normalization, which is cosine angle and volume dependent, unlike the current - independent from particles direction crossing a given surface.
The idea was to just ‘display’ 2D photon distribution but unfortunately USRBIN with fluence scoring can’t give you a meaningful quantitative outcome in terms of the photon current.