Re: Kinks in neutron momentum distribution

From: Joseph Comfort (Joseph.Comfort@asu.edu)
Date: Thu Apr 05 2007 - 18:20:19 CEST

  • Next message: me@marychin.org: "Fwd: delayed (n, gamma)"

    Hi Paola,

    Yes, plotting things this way helps to see the problem, so I'm glad I
    did it. Attached are the relevant files. The production target is a
    set of large wheels, with the beam hitting near one edge. I use a
    source.f to give unequal X and Y divergences to the beam. (It's too bad
    that the Fluka input does not have this feature.) I use mgdraw_targ.f
    to select particles in a narrow angular range, over 2pi phi angle. (For
    historical reasons, I convert to Geant3 particle ID's.) Then I use the
    program blowup.f to generate the data for plotting.

    The runs take a while. The data in the figures are for 160 million
    protons, for which I used 40 cpu processors over several days. The runs
    are collected in 40 directories (different random seeds), and 20 runs
    per directory. You will not need all of this. A single run is probably
    sufficient.

    There may be things in the input file and codings that are less than
    optimal, but I don't think any that might exist would provide a bias in
    the 20-400 MeV range. I don't know how much of an effect the 'extra'
    neutrons will have in going through a beamline collimator, or in the
    detector, but I would rather have something that I can parameterize
    better as a function for source.f.

    Thank you for looking at the issue.

    Best regards,
    Joe

    -- 
    Joseph Comfort                      Phone: (480)-965-6377
    Department of Physics & Astronomy   Dept.: (480)-965-3561
    Arizona State University            Fax:   (480)-965-7954
    Tempe, AZ  85287-1504               Email: Joseph.Comfort@asu.edu
    
    

    *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
    TITLE
    Particle production from 30-GeV protons on a Ni target
    *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
    GLOBAL 1.0
    DEFAULTS PRECISION
    SOURCE
    BEAM 40.0 PROTON
    *BEAM -30.0 -0.5 -3.88 -0.306 -0.306 PROTON
    *EMF OFF
    LOW-MAT 25.0 28. -2. 293. NICKEL
    *
    GEOBEGIN COMBNAME
      0 0 Step1 Production Target
    SPH BlakHole 0.0 0.0 0.0 3000.0
    SPH World 0.0 0.0 0.0 700.0
    SPH Shell 0.0 0.0 0.0 660.0
    SPH Vacuum 0.0 0.0 0.0 650.0
    RCC Disk1 13.0 0.0 0.00 0.0 0.0 2.17 28.0
    RCC Gap1 13.0 0.0 2.17 0.0 0.0 0.30 28.0
    RCC Disk2 13.0 0.0 2.47 0.0 0.0 1.12 28.0
    RCC Gap2 13.0 0.0 3.59 0.0 0.0 0.30 28.0
    RCC Disk3 13.0 0.0 3.89 0.0 0.0 0.83 28.0
    RCC Gap3 13.0 0.0 4.72 0.0 0.0 0.30 28.0
    RCC Disk4 13.0 0.0 5.02 0.0 0.0 0.69 28.0
    RCC Gap4 13.0 0.0 5.71 0.0 0.0 0.30 28.0
    RCC Disk5 13.0 0.0 6.01 0.0 0.0 0.59 28.0
    END
    R1bh 2 +BlakHole -World
    R2World 2 +World -Shell
    R3Detect 3 +Shell -Vacuum
    R4VacReg 6 +Vacuum -Disk1 -Disk2 -Disk3 -Disk4 -Disk5
                -Gap1 -Gap2 -Gap3 -Gap4
    R5Disk1 3 +Disk1
    R6Disk2 3 +Disk2
    R7Disk3 3 +Disk3
    R8Disk4 3 +Disk4
    R9Disk5 3 +Disk5
    R10Gap1 3 +Gap1
    R11Gap2 3 +Gap2
    R12Gap3 3 +Gap3
    R13Gap4 3 +Gap4
    END
    GEOEND
    *
    MATERIAL 0.0 0.0 0.001205 26.0 0.0 0. AIR
    COMPOUND -0.755267 7.0 -0.231781 8.0 -0.012827 20. AIR
    *
    ASSIGNMAT 1.0 1.0
    ASSIGNMAT 2.0 2.0 4.0
    ASSIGNMAT 25.0 5.0 9.0
    ASSIGNMAT 2.0 10.0 13.0
    *
    *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
    * e+e- and gamma production threshold set at 10 MeV
    *EMFCUT -0.010 0.010 1.0 12.0 PROD-CUT
    * Boundary crossing current in the middle of the target (linear bin, one-way)
    USRBDX 1.0 201.0 47.0 4.0 3.0 1. CurrUD
    USRBDX +15.0 +15.0 0.0 &
    * Call MGDRAW
    USERDUMP 101.0 2. prod
    *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
    RANDOMIZE 1.0 1.
    *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
    START 200000.0
    STOP






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