Ormarion - 5-5-2021 at 23:20
Hi, i hope everybody is doing ok. Today i wanted to share something i learnt about some years ago that i believe to be pretty interesting.
I believe when we ear about americium we all think about those smoke detector ion chamber but from what i saw at this time they also made some
lightnings rod holding quite significant sources on them (sometime they also used radium).
Have any of you ever handle or saw such things ? And how much did you measured out of it ?
Finally is the ionisation created by the rod really enough to potentially attract lightnings to it ?
PS: I am not especially planning to get one, first because no one would ever sell such thing for the purpose of it being radioactive, second because i
already have big enough sources of those isotopes.
Anyway have a great day then 
Jenks - 6-5-2021 at 07:28
Americium is an alpha emitter. The Wikipedia page on the alpha particle says that although this ionized, and ionizing, helium nucleus is typically
emitted at around 4% the speed of light (5 MeV), it can only penetrate a few centimeters of air. Since ionizing air makes it relatively conducting,
this should make sparks attempting to reach it only a few cm longer. Maybe a neat demo with a high voltage generator, but in the case of the lightning
rod it seems like the same result could be obtained by making the rod a few cm longer.
Ormarion - 6-5-2021 at 09:42
Ok interesting, in this case as radium is a alpha and gamma emitter i believe it would be a bit more efficient even if i am not sure if it worth it in
both cases. I wouldn't test myself to just strike a radioactive sources like this with a HV electrical spark lol.
Jenks - 6-5-2021 at 12:16
Now that you mention it, I suppose vaporizing spots of an americium surface with sparks isn't such a good idea. As far as radium being more efficient
(as a lightning attractor?), if this is to be due to the gamma radiation - while gamma rays go much further through air, I think they do this by
having much less interaction. So unlike leaving a conductive, unbroken ionized trail as visualized in a cloud chamber, a gamma ray would leave a trail
of isolated gas atoms too far apart to leave a conductive path. But it is all a matter of amount, right? And this reminds me of a thread I once saw on
the topic of summoning lightning either by launching a small rocket with conductive smoke into a cloud (which can work) or by firing a laser beam of
ionizing radiation into it. The problem with the lightning rod, with radiation going in all directions, is that the intensity of that radiation is
proportional to the cube root of the distance from the rod. Unlike alpha particles, gamma ray photons diverge.
[Edited on 6-5-2021 by Jenks]
j_sum1 - 6-5-2021 at 17:01
Cube root? Why not squate root?
Jenks - 6-5-2021 at 18:44
You're right - square root of the distance.
Ormarion - 6-5-2021 at 23:06
Jenks, interesting for the conductive smoke in rockets, i was thinking it would be some kind of thin wire instead but it seem more logical. If any of
you find one of those rods a day please share it under this post !
neptunium - 8-5-2024 at 14:24
It would be very difficult to find one these days. At least in Europe and the US. they have (all?) been removed starting in the mid to late 80`s
through the 90`s . They were quite hot indeed. a few millicurie of either radium in the early days, and Americium as you pointed out.
the dose rate from a lightning arrestor on the roof would be minuscule and would not add much to the background. however, it could become significant
for Radium.
However if someone wanted to take one down and store it in his/her garage or transported in a pick up, they could expose themselves to higher dose
(few tens of mRem/hours)
Holding it in your hands will definitely leave burn marks and will require medical attention in less than an hour. just sayin