Hi Araceli,
here it's not about missing cards. The default PRECISIOn thresholds are
already pretty OK to see the Bragg peak by the LINAC4 beam.
Your problems are concentrated in the scoring card.
First, you did not make a plot of ENERGY deposition, rather of PROTON
fluence (where no Bragg peak is expected, rather an abrupt fall at the
range limit).
Second, you limited your scoring to a transverse distance of 1mm from the
beam axis. This way, with your ideal pencil beam (i.e. starting with null
transverse size and no divergence), you will never see the expected Bragg
peak, since the incident beam is then enlarged by multiple scattering as
it penetrates matter. This is something everybody wishing to obtain a
Bragg peak shall well bear in mind (it's not about technicalities, it's
about basic physics concepts, as in the first exercise proposed at the
advanced course). Once the USRBIN grid covers a suitably large transverse
area, one shall still average (or integrate) the energy density over that
area [1D Projection in Flair language], and NOT extract the peak value out
of it [1D Max]. Of course, if one is interested instead in the max energy
density for stress/temperature analysis, the peak profile - though not
displaying the canonical Bragg peak - remains relevant.
Finally, in case of a Cartesian mesh, the choice of an even number of bins
in the transverse dimensions (x&y) is wrong, since the beam axis (z) turns
out to lie exactly on the bin boundary and the scored values miss the beam
center, which is shared among four bins rather than belonging to a single
central bin.
Cheers
Francesco
**************************************************
Francesco Cerutti
CERN-EN/STI
CH-1211 Geneva 23
Switzerland
tel. ++41 22 7678962
fax ++41 22 7668854
On Tue, 7 Feb 2017, Araceli Navarro Fernandez wrote:
> Hello Fluka experts!
>
> I was trying to make a plot of the energy deposition along distance of 160 MeV Protons in carbon. I would expect to find something similar to a brag peak, that is smaller deposition at the beginning, a little increase and after a small peak lower back again. I've tried with the ENECUT card and the PART-THR but I am obtaining similar results. Do I need to activate any other card? Isn't this the way to obtain a good brag peak?
>
> Sorry for the inconvenience and thank you!
>
> A.
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Received on Wed Feb 08 2017 - 00:27:15 CET