Dear experts,
I would like to know how the energy distribution (flux and/or current) of my particle source varies along its path through the different regions it passes through. Ideally, I would like to monitor this distribution over a limited surface in the plane normal (XY) to its propagation direction (Z) for any value of Z, and not only at the interfaces between two regions.
Which scoring tool should I use for this?
All the best,
Tibe
Input files
Please upload all relevant files. (FLUKA input file, Flair project file, user routines, and data files)
Thank you for your question, and apologies for the delayed reply.
If I understand correctly, you would like to monitor how the spatial particle distribution (flux and/or current) evolves as your particles pass through different regions.
In FLUKA, the most suitable diagnostic for this purpose is the USRBIN scoring card. By defining a 3D Cartesian binning, you can obtain the spatial distribution of the fluence (track-length density, in units of cm⁻² = cm/cm³) for the particle type of interest, which you can specify via WHAT(2).
Please note that USRBIN scores fluence, not current. The current represents the number of particles crossing a surface per unit area and cannot be directly obtained from a USRBIN, which is volume-based.
For a more detailed explanation of the available scoring options and the distinction between fluence and current, I recommend looking into the following presentations from the 2025 FLUKA Beginner Course:
To get a fluence spectrum - dPhi/dE - I would define a stack of regions along the beam direction. They can all have the same cross section orthogonal to the beam and a specified thickness along the beam. Between every to neighbouring regions you can then score the fluence spectrum (or the current “spectrum”). At each boundary you have the choice to score only the forward direction, or the two-directional spectrum , which would include backscattered particles.