Re: Neutron problem

From: Stefan Roesler (
Date: Wed Sep 20 2006 - 12:14:50 CEST

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    Hello Nisy,

    A few comments:

    1) Fluences were never multiplied with conversion factors due to a
    misalignment in the input, e.g.

    USRTRACK 1.0 8.0 -23. 34.14137.1669 1. AMB74-P34
    USRTRACK 0.0 0.0 &

    The SDUM must always start in column 71, otherwise my dose conversion
    factor folding would not know which set to use and return fluence

    2) Your beam energy is set at 2MeV. In principle it should always be
    higher than the highest energy set in source, i.e. 20MeV. I don't know if
    results will be really different in case of low-energy neutrons, but at
    least output files are not identical if I switch from 2MeV to 20MeV in the
    beam card. Also you upper energy limit of the Usrtrack scoring is affected
    for particles other than neutrons, e.g. in the output-file

      for 2MeV
           linear energy binning from 0.0000E+00 to 6.1337E-02 GeV, 1
    bins ( 6.1337E-02 GeV

      for 20MeV
           linear energy binning from 0.0000E+00 to 1.9489E-01 GeV, 1
    bins ( 1.9489E-01 GeV

    3) I think you would like to score photons in detectors AMB74-P12 and
    following, but what you score is indeed neutrons, e.g.

    USRTRACK 1.0 8.0 23. 12.14137.1669 1. AMB74-P12
    USRTRACK 0.0 0.0 &


    On Tue, 19 Sep 2006, Nisy Ipe wrote:

    > Hello all,
    > I have a simple neutron problem - a 252Cf source inside a tunnel with
    > concrete walls but no roof. The californium source has a dose rate
    > profile and so a source routine was written (attached). Ambient dose
    > equivalent for all particles, neutrons and photons were scored at
    > various locations using USRTRACK and compiling with ustsuw.f. Input and
    > results are attached. The results (calif. dose) read p/cmq/pr but I
    > think in my case this would be pSv/n? Multiplying the mass by 2.4 E12
    > n/g of 252Cf and the results by the number of neutrons, I obtained the
    > ambient dose equivalents at various locations.
    > If I do a simple calculation of dose transmitted through the concrete
    > wall I get results which are 6 x higher tthan the FLUKA results. So I
    > think I am doing something wrong but can't figure it out. Could the
    > experts please help?
    > Thanks and Regards,
    > Nisy

    Stefan Roesler
    CH-1211 Geneva 23
    Phone:  +41-22-7679891
    Fax:    +41-22-7669639

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