Re: Kinks in neutron momentum distribution

From: paola sala (paola.sala@cern.ch)
Date: Thu Apr 05 2007 - 10:33:17 CEST

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    Dear Joe
    Thank you very much for the new plots,
     the effect is much more visible now,
    and ... there is clearly something wrong.
    Could you please send the input file, and user routines if you have, so
    that I can have a closer look?
    Ciao
    Paola
    On Wed, 2007-04-04 at 17:49 -0700, Joseph Comfort wrote:
    > Dear Giuseppe,
    >
    > Thank you for the suggestions about the kinks in my neutron spectum. To
    > remind you, I am looking at neutrons produced by a 30-GeV beam on a Ni
    > target, about 5 cm thick.
    >
    > I reanalyzed the data in terms of neutron kinetic energy, and
    > specifically applied the binning of the 72 neutron groups, up to 19.6
    > MeV. Above that energy, I used bins that are 20-MeV wide, cut off at
    > about 6 GeV. All of the bins were put into a single array for plotting.
    >
    > The attached figure shows the results. The upper portion shows the raw
    > yields per bin vs. bin #. The first 72 bins are the neutrons below 19.6
    > MeV. For the lower fignure, I rescaled the number of events in each bin
    > so as to reflect bins of equal width (20 MeV). Then I multiplied those
    > numbers by the mean kinetic energy of the bin. I think this is close to
    > your 'lethargy' quantity. There is a kink at bin 72 (19.6 MeV), and a
    > second one near bin 90 (about 400 MeV). The yields between these bins
    > are well above the neighbors, and have an unexpected distribution.
    >
    > I want to be able to parameterize an algorithm for generating the
    > spectrum, and the kinks will make that difficult. Should I just lop off
    > the extra neutrons between 20-400 MeV, and fit a smooth distribution?
    >
    > Best regards,
    > Joe


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