Re: Thermal Neutron Capture Gammas

From: Lindley Anne Winslow (
Date: Thu Mar 22 2007 - 23:09:19 CET

  • Next message: Alberto Fasso': "Re: Thermal Neutron Capture Gammas"

    Thank you Alberto.

    I am sorry I forgot the material. I have attached my setup this time.

    It is Liquid Scintillator C9H12. I couldn't find a reference for (n,alpha) on carbon12 quickly but my understanding is (n,gamma) on hydrogen should be the dominant process. Gammas should be generated for both these materials and some are.

    The number quoted below is just the counted number of events with gammas.
    The sum of the weights of these particles is ~2100 which is the same as the weights of the incoming neutrons.

    I also see very little deuterium or carbon13 produced. When I run thermal neutrons in this environment I would expect no fewer capture gammas than neutrons entering the volume (and not escaping).


    ----- Original Message -----
    From: Alberto Fasso' <>
    Date: Friday, March 23, 2007 6:26 am
    Subject: Re: Thermal Neutron Capture Gammas
    To: Fluka Discussion <>, Lindley Winslow <>

    > Dear Lindley,
    > your question is too vague to give it an answer.
    > Which material(s) are you using? Have you made sure that
    > the cross sections of all of them include gamma production?
    > (See Chap. 10 of the Manual).
    > Are you aware that not all neutron captures produce gammas?
    > For instance you can have a (n,alpha) reaction without gamma.
    > Are you aware that in a (n,gamma) reaction you may have
    > more than one gamma?
    > Have you just "counted" the neutrons and gammas, or have
    > you calculated the sum of their weights?
    > Alberto
    > On Thu, 15 Mar 2007, Lindley Winslow wrote:
    > > Hello all,
    > >
    > > To try to understand FLUKA's treatment of low energy neutrons, I
    > > simulated 10,000 thermal neutrons (group 72)
    > >
    > > I found 5575 scatter and leave the detector.
    > > This leaves 4425 that stay in the detector.
    > > I only see 951 capture gammas from the neutrons that stay in the
    > > detector.
    > >
    > > I would expect that all neutrons that stay in the detector should
    > > capture. Is there another way to lose neutrons from the last group?
    > >
    > > Thank you,
    > > Lindley

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