vmelkon
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Am241 and beta radiation
I am talking about Am241 from smoke detectors.
I have not opened brand new smoke alarms. I have only opened ones that are ~20 y old and not working well. My geiger counter can detect beta + gamma.
It is one of those old CDV 700.
If I place the geiger's probe right on the Am241 button, I get about 1250 CPM. If I close the metal probe, the metal blocks the beta particles. It
only counts gamma. I think it goes down to 50 CPM (I don't remember).
Does it make sense that an Am241 button emits beta particles (electron or positrons?). Or is it all gamma?
Am241 decays via alpha.
The dp is Np237 which also decays via alpha and has a super long half-life.
So, essentially, there should not be any beta emitters unless there is some impurity in these Am241 buttons.
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Ubya
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Np-237 has a half life of 2 million years, seems a lot but in reality is not really a huge amount of time.
quote from wikipedia: Americium-241 decays to 237Np emitting alpha particles of 5 different energies, mostly at 5.486 MeV (85.2%) and 5.443 MeV
(12.8%). Because many of the resulting states are metastable, they also emit gamma rays with the discrete energies between 26.3 and 158.5 keV.
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vmelkon
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It would mean that Np237 turns into Pa233 which beta- decays to U233.
Is my geiger counter really detecting that much beta- particles? I have doubts.
Or perhaps it is detecting gamma radiation of weak energy, of different energy levels?
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Ubya
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Quote: Originally posted by vmelkon  | It would mean that Np237 turns into Pa233 which beta- decays to U233.
Is my geiger counter really detecting that much beta- particles? I have doubts.
Or perhaps it is detecting gamma radiation of weak energy, of different energy levels? |
as i already said, americium 241 itself emits gamma rays while decaying, alpha decay is not the only way.
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Spock
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241Am emits low energy gamma radiation and x-rays in addition to alpha particles. I'd imagine the metal shield of your probe is just attenuating the
60kev gammas. It was designed for much higher energy photons.
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vmelkon
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Thanks guys. That explains it.
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