Re: Photoneutrons

From: Alberto Fasso' (fasso@SLAC.Stanford.EDU)
Date: Thu Jul 26 2007 - 10:15:18 CEST

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    Dear Frances,

    when you use free-format input, you must input all the WHATs
    of a given command: otherwise in lines such as:
    > PHOTONUC 1.0 VACUUM @LASTMAT
    > LAM-BIAS 0.02 PHOTON
    how can the program understand if 0.02 is WHAT(1) or WHAT(2)?

    So those lines should be:
    PHOTONUC 1.0 0.0 0.0 VACUUM @LASTMAT
    LAM-BIAS 0.0 0.02 1.0 0.0 0.0 0.0 PHOTON

    or, if you don't want to input the zeros:
    PHOTONUC 1.0, , , VACUUM @LASTMAT
    LAM-BIAS , 0.02 1.0, , , , PHOTON

    Alberto

    On Wed, 25 Jul 2007, Burge, F (Frances) wrote:

    > Hello fluka users,
    >
    > Having got the gammas working I'm now looking at photoneutrons
    > generated from a 3 GeV electron beam on a tungsten target. I have a
    > vacuum region between the target and a lead shield wall.
    > I've run for 1E6 electrons, and score photons as expected in and around
    > the target. However at the moment it appears that I'm scoring
    > photoneutrons in the target and the shield wall, but not seeing any
    > neutron fluence in the vacuum between them. When I plot the results this
    > is shown very clearly as the scored neutron fluences stop abruptly on
    > the edges of the target and wall.
    > I've used the following cards to activate photoneutron interactions at
    > all energies and bias them (and using PRECISIOn as the DEFAULT):
    >
    > * Switch on gamma interactions with nuclei in all materials and bias
    > interaction length
    > PHOTONUC 1.0 VACUUM @LASTMAT
    > LAM-BIAS 0.02 PHOTON
    > * Neutron fluence around target - scored as H*(10) pSv/primary
    > USRBIN NEUTRON -28.0 190.0 0.0 3075.0AMB74
    > USRBIN 140.0 -125.0 2975.0 100.0 200.0 200.0&
    >
    > Do I need additional cards to be able to score neutrons in the vacuum
    > region?
    >
    > thanks,
    > Frances
    >
    > Frances Burge
    > Health Physicist
    > 01235 778269
    > Diamond Light Source Ltd.
    > Rutherford Appleton Laboratory
    > Chilton
    > Didcot
    > OX11 0DE
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    -- 
Alberto Fassò
SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025
Phone: (1 650) 926 4762   Fax: (1 650) 926 3569
fasso@slac.stanford.edu
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