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Spatial distribution of radiation from radioactive elements

by zephramcochran
Tags: distribution, elements, radiation, radioactive, spatial
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zephramcochran
#1
Apr11-14, 07:12 PM
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Hi all,

I have a couple questions about radiation from radioactive elements. I've read a lot of articles on the different types of radiation given off by elements undergoing nuclear decay (alpha, beta, and gamma)
but I haven't been able to answer the following question:

What is the spatial distribution of the radiation given off by a radioactive element?
Can the radiation release from an arbitrary mass of radioactive material be synchronized?

I realize this is a simple question and has probably already been answered, so if someone could either point me in the right direction on this forum or on the internet I would greatly appreciate it.
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Simon Bridge
#2
Apr11-14, 10:51 PM
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What is the spatial distribution of the radiation given off by a radioactive element?
... in general, in free space: spherical. The directions of the decay results are random.

You cannot predict the time that a nucleus will decay so you cannot synchronize decay events.
mfb
#3
Apr12-14, 10:02 AM
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Can the radiation release from an arbitrary mass of radioactive material be synchronized?
You can influence the rate of electron capture via the electron density (or get some neutrino capture events with large neutrino fluxes), but apart from those special cases you cannot change the decay rates.

snorkack
#4
Apr12-14, 10:22 AM
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Spatial distribution of radiation from radioactive elements

Quote Quote by Simon Bridge View Post
... in general, in free space: spherical. The directions of the decay results are random.
Thatīs one of the proofs that world is not symmetric: that direction of decay results is NOT random but aligned with the spin of the original nucleus.
jtbell
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Apr12-14, 10:39 AM
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See for example the experiment by C.-S. Wu in 1956 which first observed the violation of parity conservation in beta decay:

http://en.wikipedia.org/wiki/Wu_experiment
mfb
#6
Apr12-14, 11:11 AM
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Quote Quote by snorkack View Post
Thatīs one of the proofs that world is not symmetric: that direction of decay results is NOT random but aligned with the spin of the original nucleus.
Sure, but in general (and especially in free space) the spins are not aligned in some special way. The Wu experiment had very special conditions to see any effect.
Simon Bridge
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Apr12-14, 10:07 PM
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Quote Quote by mfb View Post
Sure, but in general (and especially in free space) the spins are not aligned in some special way. The Wu experiment had very special conditions to see any effect.
Thanks - saves me the trouble :)

You can make decay products fly off in any direction you want if you are prepared to go into some trouble. The Wu experiment is special - in a totally trivial way you can always just accelerate the parent objects to high velocity (in the lab), then the decay products will tend to fan out in the direction of the parent particle's travel. i.e. we have to impose some directionality on the apparatus.

But I still want to see what zephramcochran means by "synchronize".
Maybe the idea is (like) to make an antimatter-ray using beta+-decays - and OP is thinking of an analogy with lasers.
bcrowell
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Apr13-14, 01:17 PM
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Even without parity violation, the direction in which a decay product is emitted is not uniformly distributed over solid angle. Even without parity violation, the direction is correlated with the nucleus's direction of spin. Parity violation just allows a *type* of correlation that would otherwise be forbidden.
Vanadium 50
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Apr13-14, 04:58 PM
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I think a lot of people are missing the point. The radiation is strongly correlated with the orientation of the nucleus. But at room temperature, the nuclei are all in random orientations. So what comes out is random.

If you have a nucleus that emits, for example, two gamma rays - Co-60 is an example - while the directions of both are isotropic, the directions are correlated - i.e. the angle between the gammas is anything but isotropic.
Simon Bridge
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Apr13-14, 10:46 PM
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Is this what OP means by "synchonized"?


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