unphysical spectra

From: Ludwik Pienkowski (pienkows@slcj.uw.edu.pl)
Date: Wed Oct 22 2003 - 18:12:32 CEST

  • Next message: Alfredo Ferrari: "Re: unphysical spectra"

    Dear FLUKA authors,

    Thanks to Alfredo for the explanation concerning the strange cases
    that show single neutron interactions at low energy. If I well
    understand this explanation, all spectra from the neutron transport
    at low energies are expected to show unphysical shape, and only
    the average values of the variables are to be considered meaningful.

    Please look at the following test in which neutrons of two close
    energies 19.5 MeV and 19.7 MeV hit a virtually infinitely thick
    lead target. The program (attached to this email) counts the total
    energy deposition using the routine mgdraw. The energy deposition
    spectra are shown in file n2test.pdf. It is observed that only
    average energy depositions are similar for both energies
    (19.5MeV and 19.7MeV), while all other observables differ wildly.
    And so:
    1.RMS=22.7 and 9.9 MeV, for the two energies, respectively
    2.a very strange shape at 19.5 MeV and a nice gaussian shape
      at 19.7 MeV

    Moreover both spectra show a long tail. There are many events
    that show energy deposition much larger than the available energy.

     This test run is closely related to my main task for which I'm
    trying to use FLUKA. The task is to estimate the neutron detection
    probability inside a detector, for example inside a solid crystal
    cube of a volume of about 1dcm3. This probability I'm trying to
    estimate from the energy deposition spectra looking for the events
    that deposit energy inside the crystal above a given threshold.
    However, the observations from the presented test run show me that
    I'm not sure that I can use FLUKA for this purpose.

    Would you have any suggestions for me on whether and how could
    I use FLUKA to treat the above problem.

    Best regards,
    Ludwik Pienkowski

    P.S.The attached files input files:

      and energy deposinon spectra figure:

    link command:
    lfluka -o n2test -m fluka mgdraw-n2test.f

    fluka run:
    rfluka -e n2test -N 0 -M 1 -p lead n2test195
    rfluka -e n2test -N 0 -M 1 -p lead n2test197

    The results are in the files: n2test195001.log, n2test197001.log
    and n2test.pdf shows the graphs.

    Heavy Ion Laboratory
    Warsaw University
    ul. Pasteura 5A
    02-093 Warszawa

  • Next message: Alfredo Ferrari: "Re: unphysical spectra"

    This archive was generated by hypermail 2.1.6 : Thu Oct 23 2003 - 17:06:39 CEST