Dear Zhu
first of all there is a misunderstanding about the normalization of
USRBIN's by regions. The code has no obvious way to know the volume of
a region, which can be very complex.
Hence, contrary to cartesian or cylindrical USRBIN's, those by region
still have to be divided by the region volume by the user (of course it is
unfortunately the user task to calculate that volume). In your case the
(interesting) region volume is easy to calculate, it is 0.3 cm^3 (of
course you have to consider only the irradiated volume). Hence, after
dividing by the region volume, the DPA's are now 0.13/atom for 10^20
incoming protons.
This is still a factor ~2 less than what reported in the 2011 paper,
because since that time many refinements and improvements have been
implemented into the DPA calculations, particularly for particle below
threshold. Those improvements, related to the correct applications of the
xsi function (see eq. 2) in the 2011 paper) close to threshold are
responsible for the present, more correct, value.
In the attached input, which is a slight re-elaboration of your original
one, you can find a cylindrical bin (so no volume re-normalization issue)
covering the 1 cm^2 (circular) irradiation area, scoring both DPA's and
restricted NIEL. If you take the latter and apply without any "higher
order" correction the NRT formula, DPA=0.8 Tk / 2 Eth, which in this
case translates to:
DPA = 0.8 NIEL_restr(GeV/cm^3)/(2 Eth(eV))x10^9 x 55.85 / 7.87 / N_av
where 55.85 is the iron atomic weight, 7.87 its density in g/cm^3,
and N_av the Avogadro number, Eth=40 eV, you will find 0.29 DPA's for
10^20 protons (~ the old result) showing how important and delicate is
to apply the efficiency corrections close to threshold. Since DPA's
cannot be measured in reality, when comparing results among different
calulations, or referring to material properties as a function of DPA's,
it is important to be sure to use the same DPA definition/method of
calculation, hence for a "standard" NRT calculation one can always resort
to the restricted NIEL and proceed as above.
Best regards
The Fluka developers
On Fri, 30 Apr 2021, 朱雪燕 wrote:
> Dear fluka experts,
>
> I am trying to reproduce the results from the paper in the attached file.
> This is a case of 1 GeV proton on 3 mm thick Fe with a beam area of 1 m^2.
> Table 2 in the paper shows the results of the DPA calculated by fluka, which
> is 0.28 for 1E20 beam particles.
>
> My inputfile is in the attachment. USERBIN with region type was used for
> scoring. The output file print the following result:
> accurate deposition along the tracks requested
> 4.2169E-22
>
> According to my understanding, 4.2169E-22 * 1E20 = 4.2169E-2 should be the
> DPA. However, this value is one order of magnitude lower than the value 0.28
> in the paper.
>
> Could you please help to have a look if there is any misunderstanding of the
> output of fluka or there is any error in my inpufile?
>
> Thanks a lot in advance.
>
> Best wishes,
> Xueyan Zhu
>
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Received on Wed Jun 02 2021 - 10:39:42 CEST