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Problems with a simple disksource-model

  1. Jan 18, 2016 #1
    Hi,

    i'am a novice-user and use MCNP5 to simulate/generate
    pulse-high spectra.
    Herefor i try with some simple experiments [end of this post]:
    - NaI-Detector with a diameter 3cm
    - Cs-137 disksource
    i start the program with the following command:
    mcnp n=nai o=naio tasks 4

    Subsequently the three questions/problems:
    [1] is my source definition correct?
    SDEF RAD=d1 POS=0 0 0 AXS=0 0 1 PAR=2 ERG=0.66166
    SI1 0 1.5
    SP1 0 1

    [2] while running, the program plotting endless lines of
    the following messages:
    number of points to plot is less than 2. no plot.
    number of points to plot is less than 2. no plot.
    number of points to plot is less than 2. no plot.
    ..and finally:
    run terminated when 100000000 particle histories were done.
    warning. 1 of 1 tallies had bins with large relative errors.
    dump 2 on file nair nps = 100000000 coll = 12140587
    ctm = 6.06 nrn = 605478702
    mcrun is done

    [3] moreover the generatet results don't give a reliable peak at 0.662 MeV

    Can someone please help me and/or give me a hint, what
    i'm doing wrong?

    Thanks in advance!
    Ralf

    ##### input-file #####
    c define cells
    c
    1 1 -3.67 -1 2 -3 imp:p=1 $detector
    10 0 -100 #(-1 2 -3) imp:p=1 $define inside world
    11 0 100 imp:p=0 $define outside world

    c define surface
    1 cz 1.5 $define detector
    2 pz 1 $define detector bottem
    3 pz 4 $define detector top
    100 so 10 $define world

    c define source
    c Cs-137 (no x-rays)
    SDEF RAD=d1 POS=0 0 0 AXS=0 0 1 PAR=2 ERG=0.66166
    SI1 0 1.5
    SP1 0 1
    c define tallies
    mode p $photon transport
    f8:p 1 $ ??? photons on surface 1
    e8 0 1.e-5 0.1 1024i 1.0 $ 0.1Mev <-- 4096 channels --> 1.0 MeV
    phys:p 100 0 0 0 0 $ [100] ????; [1] switch of e; [1] no Bremsstrahl.
    c ***************** end of tallies
    c define materials
    m1 11000 0.15 53000 0.85 $NaI-detector
    c
    c define run time
    c
    mplot freq 50000
    nps 100000000
    c ctme 30
     
  2. jcsd
  3. Jan 23, 2016 #2
    Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
     
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