Re: About simulating neutron propagation

From: Yung-Shun Yeh (
Date: Tue Oct 09 2007 - 12:36:58 CEST

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    Dear Francessco,

    Thanks for your kindly reply. I have a low level question. If I don't care
    the waste of CPU time, can I set the DEFAULTS's SDUM to be PRECISSIO for all
    simulations? Thank you very much.

    Best regards,

    On 10/8/07, Francesco Cerutti <> wrote:
    > Dear Yung-Shun,
    > I have in fact to clarify that the choice of NEUTRONS as DEFAULTS' SDUM
    > is just intended to perform the transport of low energy neutrons (<19.6
    > MeV) within the multigroup treatment. So, coming back to your questions,
    > it is suitable ONLY for LOW energy neutrons. Since I saw that in your case
    > you have also neutron beams with energies > 19.6 MeV, for them you need to
    > perform nuclear interactions that indeed NEUTRONS neglect. Then, a
    > proper choice is either SHIELDINg or NEW-DEFA (not explicitly requested,
    > and good for MANY purposes). In the latter case, to avoid electromagnetic
    > treatment, just put the EMF card with SDUM=EMF-OFF and, to save further
    > time, put PAIRBREM with WHAT(1)=-3.0.
    > Moreover, in your input the EVENTYPE and MUPHOTON cards are useless as
    > well.
    > Finally, to perform one million histories, it is better to split them into
    > more cycles/runs (rfluka allows you to perform independent cycles in
    > sequence), this way you will have also the possibility of getting
    > statistical errors comparing the unformatted results of different cycles
    > with the standard postprocessing tools (e.g. usxsuw for USRBDX).
    > Thanks a lot to Alberto for pointing out these issues.
    > Cheers
    > Francesco
    > **************************************************
    > Francesco Cerutti
    > CERN-AB
    > CH-1211 Geneva 23
    > Switzerland
    > tel. ++41 22 7678962
    > fax ++41 22 7668854

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