RE: thick target spectra from USRYIELD

From: Alfredo Ferrari (alfredo.ferrari@cern.ch)
Date: Mon Dec 19 2005 - 11:16:05 CET

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    Hi Frances

    the 511 keV line is indeed there, but masked by your (toow wide) choice
    of bin widhts.

    In the attached plot you see:

    a) red: the photon spectrum with your USRYIELD cards
    b) green: the same with
    USRYIELD 2399.0 7.0 -23.0 1.0 2.0 1000.0 PHOTYIELD
    USRYIELD 10.0 1.0E-5 120.0 90.0 0.0 3.0 &
        where the 511 line is already pretty visible
    c) black: the same with
    USRYIELD 2399.0 7.0 -23.0 1.0 2.0 1000.0 PHOTYIELD
    USRYIELD 10.0 1.0E-5 120.0 90.0 0.0 6.0 &
        where now photons are inverse cosine weighted (--> fluence like
        and not current like) which is almost surely the right case if the
        experiment reports the results in ../cm^2 and "cm^2" are as customary
        "per unit NORMAL area" (or per steradian). If you send me the
        experiment ref. I can check if this is really the case.

                             Ciao
                            Alfredo

    On Mon, 12 Dec 2005, Burge, F (Frances) wrote:

    > Sorry about the unreadable message - hopefully this will be better.
    >
    > I am trying to calculate a photon spectrum behind a 2.5cm thick copper
    > target, on which a 6GeV electron beam of radius 1cm is incident. Since
    > the results required have units of [photons/energy /cm2] I am using the
    > USRYIELD card to calculate a plain double differential yield with
    > respect to energy as the first quantity and polar angle in degrees as
    > the second. I have set limits on the angle between 0 and 90 degrees as I
    > guess this includes everything in the 'forward' direction, and score the
    > photons crossing from the end of the target region into a detector
    > region.
    >
    > The problem is that my output spectrum doesn't seem to include the peak
    > at 0.511MeV for annihilation photons. The peak I get is somewhere
    > between 0.1 and 0.2MeV. The published results which I am attempting to
    > reproduce show a clear peak at 0.511MeV. I have set transport energy
    > cut-offs in the peg file (still using FLUKA2003...) as:
    > AP=0.001 UP = 6000
    > AE=0.521 UE = 6000.511
    >
    > I have attached the input file. Can anyone tell me why I don't see the
    > 0.511MeV peak? In case the attachment does not make it through, my
    > USRYIELD cards are:
    >
    > *photon double differential yield (per energy per polar angle)
    > USRYIELD 2399.0 7.0 -23.0 1.0 2.0 1000.0
    > PHOTYIELD
    > USRYIELD 6.0 1.0E-5 40.0 90.0 0.0 3.0
    > &
    >
    > Region 1.0 is the copper target and region 2.0 the detector region which
    > has the same (1cm) radius as the target and is 3cm long.
    >
    > many thanks,
    >
    > Frances
    >
    > Frances Burge
    > Health Physicist
    > 01235 778269
    > Diamond Light Source Ltd.
    > Rutherford Appleton Laboratory
    > Chilton
    > Didcot
    > OX11 0QX
    >
    >

    -- 
    +----------------------------------------------------------------------------+
    |  Alfredo Ferrari                ||  Tel.: +41.22.767.6119                  |
    |  CERN-AB                        ||  Fax.: +41.22.767.7555                  |
    |  1211 Geneva 23                 ||  e-mail: Alfredo.Ferrari@cern.ch        |
    |  Switzerland                    ||          Alfredo.Ferrari@mi.infn.it     |
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