Re: Do gamma rays leave "partice" tracks?

Tom Roberts wrote:
billb@xxxxxxxxxx wrote:

On Dec 13, 11:00 pm, ar...@xxxxxxxxx (Murray Arnow) wrote:

Gammas don't produce ion trails. [...] The delta rays can be analyzed
for information about the primary ionizing agent.


That's more like the idea I was after. I imagine that the trajectory
of the resulting deltas would be mostly unrelated to the direction of
the incoming gammas which produced them.


No. For a charged particle traversing matter, the delta rays are emitted
in a direction very close to the direction of the charged particle.
Note, however, that they are very low energy and multiple scatter a lot
(which changes their direction), and don't have much range.

Note: "delta ray" is an old-fashioned term for a low-energy
electron kicked out of a material (typically they have a few
keV energy, but can occasionally be up to an MeV or so); the
term is not normally applied to higher energy electrons.

But a gamma can produce only a single electron (the term "delta ray" is
not normally used for this) or an electron-positron pair. A gamma with
several MeV energy would produce a several MeV electron, which would
immediately shower.


Tom Roberts


An indication of the extremely high optical 'X-ray laser' energies
(intensity 10^22 watt/cm^2 and electric field 10^17 volt/cm )
required for 'Schwinger' pair production
are indicated:
http://arxiv.org/abs/nucl-th/0511085

The latest powerful lasers (XFEL) are enlisted to study such
EM pair production effects.

Richard D. Saam

.

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