Why straggling appears

[abotiz]

Hi!

I would like some clarification about the straggeling phenomena, why the tip of the curve is pointy ( stiff ) att the topp for 1 particle, but for several particles the top is rounded off.
29680

I founf Wikis explanation a little bit dry, or perhaps that is the only way to describe it?


http://en.wikipedia.org/wiki/Range_(particle_radiation)

" [...] a range may be well defined for that radiation, depending on its energy and charge, as well as the ionisation energy of the stopping medium. Since the nature of such interactions is statistical, the number of collisions required to bring a radiation particle to rest within the medium will vary slightly with each particle, i.e. some may travel further and undergo less collisions than others. Hence, there will be a small variation in the range, known as straggling."

Thanks!

[Bob S]

Here is a quote from Evans The Atomic Nucleus, (McGraw Hill) page 660

"Identical charged particles, all having the same initial velocity do not all have the same range. The observed ranges of individual particles from any monoenergetic source will show a normal (gaussian) distribution about the mean range. As early as 1912. Darwin correctly identified this distribution as due to statistical fluctuations in the individual collisions between the charged particle and atomic electrons, and named the effect range straggling."

Evans then goes on to derive both range and energy straggling statistically, on pages 660-667. few other authors go into as much detail as Evans.

As you may recall, the Bethe-Bloch dE/dx energy loss equation is based on many collisions between the charged particle and atomic electrons (and not the nucleus).

Multiple scattering IS caused by the charged particle scattering off the nucleus (Coulomb scattering).

Bob S

[abotiz]

Thank you for you reply.

I understand this much better

Thanks!