Re: energy binning when scoring neutron fluence spectra with USRTRACK

   Dear Zuzana,

the logic is a bit different. USRBDX, USRTRACK, USRYIELD when requested
to score NEUTRONS (fluence or current) or a generalized particle that
contains also the NEUTRONS (e.g. ALL-PART) then FLUKA creates two histograms

1. From Ehigh to Elow with the with a logarithmic step (if log is
requested) of
      DLE = [log(Ehigh) - log(Elow)] / N
if N=the bins requested

However if Ehigh>20MeV there will be ONLY
      N(>20MeV) = [log(Ehigh)-log(20MeV)] / DLE
bins above the 20MeV with the
trunc(N(>20MeV)) being complete bins
plus one (if not properly aligned) smaller bin from 20MeV to the closest
bin boundary

2. A histogram corresponding to the neutrons groups from the 1st group
if Ehigh>20MeV down to the last group if Elow<=1e-14GeV, otherwise to
the group that contains the Ehigh and the Elow.

Therefore if you want 57 log bins from 20MeV up to Ehigh plus the 260 groups
then you should calculate the
      DLE = [log(Ehigh)-log(20MeV)]/57
Find the number of bins corresponding to the limits from 1e-14 to Ehigh
      N = [log(Ehigh)-log(1e-14)] / DLE
and make a final adjustment to the Elow limit such as to be on a bin
boundary
      log(Elow) = log(Ehigh) - ceil(N)*DLE

Hope that helps
Vasilis

On 08/12/10 10:33, Zuzana Zajacova wrote:
>
> Dear FLUKA forum,
>
> I would like to obtain a certain energy spectrum when scoring fluence of=20
> neutrons with USRTRACK. The spectrum should have 57 logarithmic energy=20
> bins above 20 MeV - so I ask for 260 + 57 =3D 317 energy bins. Instead, I=
> =20
> get 260 + 101 energy bins (see the attached output file). Is this a bug=20
> or is this due to some logic based on which bin sizes are now determined=20
> in case of neutrons =85? Do I have to add another scoring specifically for=
> =20
> neutrons above 20 MeV to obtain the desired binning?
>
> Thanks,
> Zuzana
Received on Sun Aug 15 2010 - 20:02:50 CEST