Hello Jia,
Since you are concerned about the energy deposition, the appropriate card in FLUKA is the USRBIN card with the ENERGY option for the scoring. It will provide you the energy deposition per unit volume in the mesh you require.
Now, since you question is just focused on the transverse beam size of the energy deposition, there are two viables option:
- You can collect the energy deposition matrix from the FLUKA simulation and postprocess the data.
- You can exploit the 1D Trace-H & 1D Trace-V plots in the flair interface (give a look at this discussion: Question on USRBIN plot "Type")
To further comment about the latter, the 1D Trace plot will provide the position of the maximum and the FWHM (remember to correct it to the rms beam size). Since you are interested only in the beam size you will need to just import this quantity and plot it against the longitudinal coordinate.
Taking the input file from your previous question (Peak energy deposition density and longitudinal power - #5 by dcalzola) I was able to give you a quick example of what I mean:
ILC_dcalzola_trace.flair (2.1 KB)
As you can see, the USRBIN you can adopt is a normal X-Y-Z binning.
In the plot section, I have chosen to check the horizontal beam size around y=0, and the agreement with your plots is acceptable, considering that my cuts for the simulation are extremely rough.
The only downside point of this procedure is that you will not have any statistics of the FWHM produced, at least to my knowledge.
Let me know if you have any further doubts.
Cheers,
Daniele