Photoneutrons

From: Burge, F \(Frances\) (frances.burge@diamond.ac.uk)
Date: Wed Jul 25 2007 - 18:11:02 CEST

  • Next message: Mr. Bhushankumar Jagnnath Patil.: "biasing option"

    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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