Re: about RAY

From: Alberto Fasso' (fasso@SLAC.Stanford.EDU)
Date: Fri Jan 14 2005 - 21:31:44 CET

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    Dear Wu Zhen,

    On Fri, 14 Jan 2005, wuzhen wrote:

    > Dear Fluka users,
    > I want to use RAY pseudoparticles, but there is a error I can't deal with.
    > I have a normal input file, which result is correct. I change the source
    > particle's name from PHOTON to RAY.
    > But in my output file, when the first particle is transported, a error
    > occured.
    > *** Phxsec: have you got the right mat. data set?
    > I don't know why?

    This message means that you have met a photon with an energy higher than
    the upper limit of the cross section table produced by PEMF.
    You should do again the pemf file with higher energy limits.

    > My pemf file works normally in the normal input file. Should I do any other
    > change about input file or pemf file???

    I guess that your primary beam energy, and your upper energy limit in PEMF,
    are lower that the "Compton minimum". But RAY transport requires computation
    of ALGTOT, the cumulative distance traversed in units of maximum photon
    mean free paths at Compton minimum. Therefore, your pemf file must be
    made again for an upper limit at least as high as the Compton minimum.

    > And:
    > I want to got the probability that a photon transport from source to detector
    > without any scattering. Can I use the RAY to get ALGTOT.
    > And use the formula P=exp(-ALGTOT) ? Is it right?

    That formula is valid only at an energy equal to Compton minimum.
    Not at other energies.


    Alberto FassÚ
    SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025
    Phone: (1 650) 926 4762   Fax: (1 650) 926 3569

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