Re: [fluka-discuss]: momentum Spread in source.f

From: Stefan E. Mueller <stefan.mueller_at_hzdr.de>
Date: Fri, 5 Mar 2021 13:31:36 +0100 (CET)

Dear Lawrence -

according to the manual, WHAT(2) of the BEAM card gives the beam momentum
spread in GeV/c as FWHM of a Gaussian momentum distribution (if WHAT(2) <
0.0).

I could reproduce the distribution created by your BEAM card by setting

          CALL FLNRRN(RGAUSS)
          PMOFLK (NPFLKA) = PBEAM*(ONEONE + 0.005 * RGAUSS)

in the source.f-file (and in consequence, since kinetic energy and
momentum are not independent, I set

          TKEFLK (NPFLKA) = (SQRT (PMOFLK (NPFLKA)**2 + AM (IONID)**2 )
      & - AM (IONID))
).

That said, I was expecting (like you) that I would have to scale the
fluctuation around "ONEONE" by 1./2.355 to account for the fact that in
the BEAM card, a FWHM of 0.005 GeV was given, which should correspond to a
standard deviation of sigma = 0.005 GeV/2.355. But apparently, this is not
the case. Maybe FLUKA users in the list more expert on this than
myself could comment on that.

Cheers,

         Stefan

--
Stefan E. Mueller
Department of Information Services and Computing - Computational Science
and Institute of Radiation Physics
Helmholtz-Zentrum Dresden-Rossendorf
Tel: +49 (0351) 260 3847
Stefan.Mueller_at_hzdr.de
http://www.hzdr.de
Vorstand: Prof. Dr. Sebastian M. Schmidt, Dr. Diana Stiller
Vereinsregister: VR 1693 beim Amtsgericht Dresden
On Fri, 5 Mar 2021, 董思学 wrote:
> 
> Dear FLUKA experts,
> 
> I want to implement the same momentum spread in source routine as it in
> flair.
> 
> [IMAGE] But I failed to set it in source.f like this.
> 
> [IMAGE]
> 
> So I really want to know the correct way to do that .
> 
> Many thanks in advance, regards
> 
> Lawrence
> 
> 2021.02.27
> 
> 
> 
>



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Received on Fri Mar 05 2021 - 15:19:46 CET

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