Dear FLUKA experts,
I am trying to understand how FLUKA determines the volume when calculating
dose in USRBIN (228). Does FLUKA calculate the energy deposited in a volume
element, then divide by the volume of that element to get the dose?
I ask because for a dose binning into volume elements in
cylindrical coordinates with symmetry in θ a volume element ends up as
V=dzπ(r2)^2-dzπ(r1)^2.
For a proton (or other charged particle) beam incident normal to the end of
such a cylinder (in the z direction) one expects a gaussian fluence
distribution in n r due to coulomb scattering. The energy should therefore
be normally distributed along the fluence distribution as it passes through
each cylinder element with thickness dz.
The volume of each cylinder element increases with r, however, and dividing
the energy deposited in each element by the volume of that element produces
a dose distribution which is non-gaussian in r.
However, when scoring dose distribution using USRBIN in FLUKA, I
consistently obtain gaussian distributions in r.
So my question is, am I considering FLUKA's dose calculation wrongly in
that energy deposited in each volume element are not divided by the volume
of each element? If not, then what volume is considered for the dose
calculation? Is it the volume of the entire region to be scored?
Thanks very much for your kindly assistance.
Ryan Brosch
Arizona State University
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Received on Tue Jun 15 2021 - 17:27:06 CEST