Re: path length vs. distance traveled

[huntjb@ornl.gov (Jerry Hunt)]

There's a very good discussion of some of these terms ("range" is one not
mentioned) in Jim Turner's "Atoms, Radiation, and Radiation Protection" and
in ICRU 37.

At 10:30 AM 1/7/98 -0600, you wrote:
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>I am reviewing some Health Physics training materials and came across a
>section that I found confusing. When discussing LET, stopping power, and
>specific ionization, the text uses "path length," "distance of travel,"
>"track," and "depth of penetration" interchangeably. When I went to my usual
>sources to verify my recollection of the meanings of these terms, I ended up
>more confused than I started out.
>
>My recollection is as follows:
>
>path length: the linear distance from the start point of the charged
>particle's path to its end point.
>
>distance of travel: the actual distance traveled by the particle from the
>start point of the particle's path to its end point. 
>
>track: the actual path taken by the charged particle.
>
>depth of penetration: the linear distance from a charged particle's point of
>entry into an absorber to its path's end (path length in absorber).
>
>  ___                   ___
>   |      *\             |
> p |       /             |<--depth of penetration
> a |      /<--track,     |
> t |      \   distance   |
> h |    |\ \ of travel   |
>   |    | \/             |
> l | ____\_______________|__absorber
> e |     /
> n |    / /\
> g |    \/  \
> t |        /
> h |       /
>  _|_     *   
>
>(sorry if the graphic doesn't work - try a monospaced font if it gives you
>problems)
>
>Are these correct? If not, where can I find a clear explanation of the
>terms?
>
>Thanks,
>Gary Damschen
>damschenga@mkf.ornl.gov
>
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Jerry Hunt, CHP
Office of Radiation Protection
Oak Ridge National Laboratory
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Ph.-(423)576-5117, Mailto:huntjb@ornl.gov
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