Questions concerning LAM-BIAS and MATERIAL

From: John Clem (clem@bartol.udel.edu)
Date: Wed Jun 23 2004 - 16:22:15 CEST

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    Dear All,

    I have a couple of questions:

    1) I'm directing a beam of 20GeV protons vertically into the atmosphere
    and recording the neutrons and muons that reach sea-level. LAM-BIAS is set
    at -0.5 for inelastic biasing. To determine the effectiveness of LAM-BIAS,
    the number of weighted neutrons above 20MeV are counted. Each run has 1000
    20GeV protons...

    Run# Number of Neutrons >20MeV
    1 74.4391111
    2 97.5083734
    3 78.7172711
    4 83.6408111
    5 65.2695326
    6 79.2154181

    Ave 79.79842
    RMS 9.744451

    Muons >500MeV were also collected at Sea-Level

    1 201.015869
    2 214.285889
    3 212.272003
    4 204.647949
    5 193.411865
    6 189.782959

    Ave 202.56942
    RMS 8.995406

    The run to run variation seems higher than expected. In the case for
    neutrons this suggest 600000 20GeV Protons at LAM-BIAS = -0.5 would be
    needed for a ~1% statistical error. I would have expected faster
    convergence using this BIAS method, however I am new to this feature. Is
    this what I should expect ??

    2) How will changing the ISOTOPE number in the MATERIAL card effect low
    energy neutron propagation ?? Does it only effect nuclear parameters such
    as the cross-sections, multiplicity and kinematics at higher energies ?

    Thanks,
    John


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