Dear FLUKA experts,
I am studying the neutron yield from a Be target hitten by a proton beam.
In particular, right now I am trying to reproduce the results of this paper
http://arxiv.org/pdf/1208.1713.pdf.
I run a FLUKA simulation with the same configuration: a cylindrical Be
target (diameter: 3.5 cm, length: 3 cm) hitten by a 62 MeV proton beam and
surrounded by 3 mm carbon fiber (for the record: I took into account also
the carbon fiber in the simulation, however I verified that its presence
makes no difference for the final result), please find the input card in
the attached file.
I used a USRYIELD card to scrore the total number of neutron produced. The
first variable is the polar angle theta (in degree, from 0 to 180; only 1
bin), the second the kinetic energy (from 0 to 1 GeV). I used also a
normalization factor of 0.0795775 (=1/4Pi): in this way the number reported
in the output of the USRYIELD card ( file *NeutronYield-62MeV001_fort.21*) is
exactly n/p (is it correct? Did I made a mistake in the USRYIELD card?)
I found a value of n/p of 6.8%, while in the paper they report an
experimental value of 11.7%: there is almost a factor of 2. The total
number of protons is 10^8, so the statistical fluctuations (estimated as
sqrt(Nn), where Nn is the number of neutrons) should be around 0.002% and
cannot explain such a tension.
- I used DEFAULT: PRECISIOn
- I activated the PHYSICS: COALESCEnce card (WHAT(1)=1001), EVAPORATion
and IONSPLIT
- I also activated the PHOTONUC and IONTRANS cards
Is there something I am missing? Do I need to activate other cards?
The other USRYIELD cards are used to reproduce the plots in the paper,
where are reported the energy/angular distribution, for fixed values of the
angle/energy. In the file *AndDist.pdf *you can find the angular
distribution at 5 different energies: the solid curves are the results of
the simulation, the dashed curves are the data from the paper: you can see
that, while the behaviour is compatible, there is a difference in the total
normalization, expecially at low energies (0.5 MeV).
Do you know why I find such a tension with the results in the paper?
Thank you very much for your help
Emilio Ciuffoli
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Received on Sat Apr 16 2016 - 07:25:33 CEST