Re: Proton stopping powers in water

Dear Dan
sorry for the delay in the answer.
Actually it is true that the work that you quoted was not yet included
in the general FLUKA distribution.
FLUKA developers did not make any progress in this respect for different
reasons:
a) ICRU tables are for a given material, also compounds (take water):
in order to use those tables, FLUKA should recognize that the material
that the user calls WATER (or whatever) is really "water" and that the
different atoms (elements) that build such compound really belong to such
a molecule.
b) There is an issue that people is debating at present: ICRU tables are
using as ionization potential for water 75 eV. Now there are claims that
this value has to be increased. Before starting the work needed by
previous point a) we are waiting for a this thing to be settled to avoid
to redo the work many times
c) we evaluated that the region where you find differences gives a
negligible contribution in terms of range of particles, and that therefore
there is no significant effects in most of the problems we are treating
and in particular for particle therapy. I admit thet there could be some
exception for very particular tasks.

        Best regards
                Giuseppe

On Mon, 9 Mar 2009, Dan Kirby wrote:

> Dear Fluka team,
>
> I enquired about proton stopping powers at the beginning of February, but
> nobody responded. so forgive my persistence but I would like to re-ask the
> main part of my previous submission to the mailing list:
>
> I was under the impression that Fluka stopping powers in water were
> parameterized so as to follow ICRU recommendations, after seeing the paper:
> "Improvement of low-energy stopping power algorithms in the FLUKA simulation
> program" by Parodi and Squarcia, Nuclear Instruments and Methods in Physics
> Research A 456 (2001) 352-368.
> According to this, a new parameterization was integrated into Fluka so that
> water stopping powers were within 1% of ICRU values for all energies.
> However when I print them out, I see differences of about -5% compared to
> ICRU in the range 1-300 MeV, and up to 30% between 1keV - 1MeV for the same
> I value (75 eV) recommended by ICRU. The plotted values looks just like the
> "old Fluka" plot in fig. 8 of the above paper.
>
> Did I misunderstand this paper - was this change to stopping powers not
> actually implemented into the main Fluka release?
>
> I attach a plot of Fluka vs ICRU stopping powers, using the latest Fluka
> respin.
>
> Best wishes,
> Dan
>
> Dan Kirby
> Medical Physics Group
> School of Physics and Astronomy
> University of Birmingham
> Edgbaston Park Road
> Birmingham B15 2TT
> UK
> +44 (0) 121 4144714
>
>
>
>
Received on Wed Mar 11 2009 - 14:15:57 CET