Roman,
please find inline answers to your questions.
Best regards, luigi
On 13 Aug 2015, at 08:36, Roman Savinov <rsavinov_at_calpoly.edu<mailto:rsavinov_at_calpoly.edu>> wrote:
Mikhail,
thank you for your response.
about example with protons:
1) Is it true that primaries, by which I need to multiply the Y-axis of the fluka plot to match the plot of the original source, are just the number of particles (protons in this case) which fluka track during transport?
It’s not true. The number of FLUKA primaries affects only the quality of the results. You want to have a reasonable small statistical uncertainties from the simulation.
AS FLUKA results will always be expressed “per primary”, then it’s up to you to compute the correct normalisation factor.
And this factor is not connected in any way to the number of primaries you simulated.
[And indeed it seems you have simulated 5e5 primaries (from one of your previous e-mail) but then the normalisation factor is 1.84393E+10.
More explicitly if you simulated 10 times (or 1000 times) more primaries, you will have to use the same normalisation factor]
The value 1.84393E+10, that you found, has units of protons/cm^2 so when I multiply it by the cross sectional area of the target the plot matches perfectly!
about example with photons:
source_sahani.dat = [ Gev photons/sec ]
When I do f_tot=f(Emax)-f(Emin) for the photon_spectra, the plot is way off.
2) How do I find Ftot (or primaries) in photon_spectrum?
as I’ve just said, it’s up to you to compute the correct normalisation for your problem.
Also for the photons, you should apply a similar procedure that was described in the last Mikhail’s e-mail. But now you do not have
any more an analytical expression, but a discrete distribution.
However, I’m afraid you cannot extract this information from Fig. 1 from Sahani’s paper. The vertical reads photons/s and not photons/GeV/s,
therefore you cannot compute the integral (or better the sum in this case) unless you know the bin width they used.
3) Also, where in the source.f do I tell fluka what is the physical meaning of the 2nd column of the source_sahani.dat?
Please give a look also at the slides 34-36 of this lesson<
https://indico.cern.ch/event/334606/contribution/35/attachments/653364/898409/AdvancedSources2014.pdf> from the last advanced course (it’s the same presentation that Mikhail pointed you before).
4) Does the output of USRTRACK is always Part/GeV/cmq/pr for diff. fluence and Part/cmq/pr for integral fluence no matter what the unit of the source spectrum?
Please see Note 1 of the USRTRACK command in the FLUKA manual. if you are sampling from a discrete distribution or an analytical function,
this’s not going to change how the result is expressed by USRTRACK.
5) if the energy intervals in source_sahani.dat is not constant, does it affect anything?
yes, it does. For a discrete distribution, the normalisation is given by
[cid:2027D89E-253E-46F6-8347-101586BD9671_at_cern.ch]
where the sum is over all the bins. Different bin widths matter. But as I wrote before, the vertical axis of Fig. 1 read Delta_N and not Delta_N/Delta_E.
Therefore you will end with a different sum if you digitise the plot from the paper with 58 points or 10 or 1000...
thank you
Roman
<photon_spectrum.tar.gz>
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Received on Thu Aug 13 2015 - 14:30:24 CEST