From: me@marychin.org
Date: Tue Jan 09 2007 - 22:07:39 CET
Many thanks Alberto (and Marta, who gave a similar reply). No, I don't
have any sophisticated problem at hand that potentially challenges the
assumptions, I'm only doing modest medical physics applications. It's
just something which has been bugging me for years, which I haven't been
able to nail down with strong arguments :)
Cheers,
mary
Alberto Fasso' wrote:
>Dear Mary,
>
>there is no "specific principle / theory": it is just that in nearly
>all applications one can think about, these effects are so small that
>they can be safely neglected. The density of particles from most sources
>is many many orders of magnitude smaller than the density of the most
>rarefied gases. Taking into account the interactions between different
>histories would spoil the linearity of normal Monte Carlo (results would
>not be just proportional to number of histories, but would be dependent on the
>source intensity). A similar lack of linearity can arise if we want to account
>for the changes in material composition due to the irradiation (e.g. plutonium
>production in a reactor). It is not impossible to do it in principle: some
>specialized codes do it, but one has recourse to this kind of increased
>complexity only if there is an actual necessity.
>
>Are you just interested in this problem for theoretical reasons, or do
>you have an application in mind? Probably there could be an interest
>in some astrophysical problems, but I would not recommend using FLUKA
>to to track particles in the center of the Sun :-)
>
>Kind regards,
>
> Alberto
>
>
>On Tue, 9 Jan 2007, me@marychin.org wrote:
>
>
>
>>Hi.
>>
>>Could someone help me explain:
>>1. Presumably particles from a source don't interact with each other -
>>otherwise serial and independent computation of each radiation history,
>>as practiced in Monte Carlo simulations, wouldn't be valid. Why?
>>
>>2. Presumably radiation histories do not perturb each other - otherwise,
>>as above, the way we do Monte Carlo simulations won't make sense. Why?
>>
>>What specific principle / theory can I use to support statements such as
>>these?
>>
>>Many thanks,
>>mary
>>
>>
>>
>>
>
>
>
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