RE: Problem with deuton converter

From: Stefan Roesler (
Date: Tue May 15 2007 - 17:59:24 CEST

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    Dear Vincent,

    In addition to what Sebastien wrote (i.e., there is no model for nuclear
    interactions below 100MeV/nucleon in the distributed version) you are
    PHYSICS 1.0 0.001 IONSPLIT

    which splits the deutron into its nucleons before being transported. This
    way you always get at minimum one neutron, which is unphysical in this


    -----Original Message-----
    From: on behalf of Sebastien WURTH
    Sent: Tue 5/15/2007 5:28 PM
    To: Feracci Vincent
    Subject: Re: Problem with deuton converter
    Hello Vincent,

    Your beam energy is too low to get interactions through DPMJET (it is
    transparent here). I did a SPIRAL2 simulation with FLUKA, and although
    it wasn't the purpose of my study, I scored neutron fluence in the
    converter (a cylinder of 7.7 cm radius and 1 cm thick) : 2.17e+14
    n/cm²/s (with usrtrack then) and coming out from converter (usrbdx over
    4 pi) : 1.17e+14 n/cm²/s. My beam was not cylindrical but rectangular
    3cm*3cm, 40 MeV, 5 mA (ie 3.125e+16 d/s).
    I found that is was not so far of the given values for 2.83 and 4 cm
    beam diameters respectively 1.1e+14 and 7e+13 n/cm²/s.
    I read that the neutron yield should be ~2.5% per deuteron over 4pi.


    Feracci Vincent a écrit :

    > Hello Fluka users,
    > I am simulating the bombardment of a cylindric graphite converter (8
    > cm diameter, 1 cm thick) by a 40 MeV deuton beam (gaussian spatial
    > repartition) in order to produce neutrons. However in my simulation I
    > measure a convertion factor which is close to 1 ( 1 deuton creates 1.1
    > neutron) while it should be, according to other simulations and
    > experiments about 0.01. In order to take into account deuton
    > interaction, I used the following parameters:
    > EVENTYPE 2.0
    > DPMJET (i have linked the DPMJET library)
    > PHYSICS 1.0
    > PHYSICS 3.0
    > PHYSICS 1.0 0.001
    > LOW-NEUT 72.0 22.0 0.0196 1.0
    > I used Usrtrack and Usrbdx to measure fluence inside the converter and
    > at given angles of the incident deuton beam. I run my calculations on
    > FLAIR V0.4 and simulated with 20.000.000 primaries separated in 50 runs.
    > I am unsure of the physics models I have used but I can't manage to
    > understand what is wrong with my simulation. I have attached my input
    > file to this mail. Is it a problem of energy threshold for the deutons
    > who by consequence all split to give neutrons?
    > Thanks in advance,
    > Vincent Feracci
    > Intern at the GANIL on SPIRAL2 project

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