Re: neutron scattering (2)

From: Alberto Fasso' (fasso@SLAC.Stanford.EDU)
Date: Fri Jun 20 2003 - 19:52:16 CEST

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    You have posted these questions already, but I have not answered before
    because I don't know the answer to all of them. But since nobody
    else has reacted, I will at least give you the easy ones.

    On Fri, 20 Jun 2003, Bernhard Schwingenheuer wrote:

    > Dear FLUKA community,
    >
    > I am using FLUKA for neutron scattering (9.5 MeV) in nitrogen N14.
    > In USDRAW I try to learn s.th. about the implemented scattering
    > processes for ICODE=300.
    > A few questions come up when I look at the information I get:
    > 1) Is the information stored in the common block RESNUC meaningful at
    > the entry USDRAW with ICODE=300 ?

    Yes. (If you look in the manual at the list of isotopes present in the FLUKA
    neutron library, for 14N there is a "Y"(es) in the "RN" (Residual Nuclei)
    column).

    > 2) for those reactions when NP=2 and the 2 secondaries are neutron +
    > gamma I find that the sum of outgoing energies is typically 2 MeV larger
    > than the neutron energy before the scattering. If these are inelastic
    > reactions then I expect to have N14 before and after the scattering and
    > hence energy should be conserved (averaged over many reactions).

    I don't know this one. Maybe I should do some tests.

    > 3) For thermal neutrons I see some cases with NP=2 and the secondaries
    > are neutron + proton!!
    > The proton energy is always 0.58 MeV (= 13/14 of the Q value of (n,p)
    > reaction for N14). Typically there are several of these reactions for a
    > given beam particle! One neutron makes several (n,p) reactions???

    I don't know about NP=2 and secondaries = neutron + proton (or maybe is
    there hydrogen in addition to nitrogen?).
    Concerning one neutron making several (n,p) reactions, it is possible, if
    you have non-analog absorption set up for the thermal
    group. See more information in the description of option LOW-BIAS.
    If you don't want this feature, issue a command LOW-BIAS with
    WHAT(2) = 73. for the regions of interest.

    > 4) what is the meaning of the RESNUCLEi output if I have only 1 beam
    > particle, i.e. "START 1."?

    It means "number of residual nuclei (of a given type) per incident
    particle weight", whether you have only 1 beam particle or more.
    If the beam particle has weight 1 (the most common case), then it means
    "number of residual nuclei produced by that particle".

        Alberto FassÚ

    -- 
    Alberto FassÚ
    SLAC-RP
    P.O. Box 4349, MS 48, Stanford CA 94309
    fasso@slac.stanford.edu
    

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