randomdreams: riding up mini slickrock (Default)
[personal profile] randomdreams
Anyone here know much about theraputic/pharmaceutical radiochemistry?
Palladium-103 decays by electron capture from an inner shell, which emits an electron neutrino, and subsequently emits an x-ray when another outer electron falls into the hole where the previous one had been.
But we are definitely detecting a ton of beta particles coming off my friend. (As in, the geiger tube with the beta window closed detects about half as many particles as when it's open.)
Scattering from subsequent impacts of ionizing radiation?

Date: 2017-06-16 05:35 am (UTC)
corvi: (Default)
From: [personal profile] corvi
Did you ever say why your friend is radioactive?

Date: 2017-06-16 04:13 pm (UTC)
gfish: (Default)
From: [personal profile] gfish
I don't think it's polite to ask.

Date: 2017-06-16 08:33 am (UTC)
From: [personal profile] eub
Yeah, I'm no expert, but those photons being ionizing are going to kick some electrons off atoms. https://en.wikipedia.org/wiki/Secondary_electrons
I had the impression though it tended to shake off a lot of near-thermal electrons more than dumping its energy into one or two.

When a Geiger counter is detecting betas, what's its energy floor? This random instrument says down to 0.2 MeV betas.

The Pd's X-ray is going to be... jeez, Wikipedia doesn't make this easy for a bozo to find energies from K-capture. Okay I think that will be probably the photon from L falling to K, i.e. the K-alpha line, which Pd has at, huh, just 21.2 KeV? (Sanity check: 1.24 / 21200 = 5.8e-5 microns = 0.058 nm which is on the hard end, okay.)

That 0.02 MeV is actually right at the limit for that device detecting gammas. So unless ten of them gang up on one electron, they're not making betas you can detect. So huh.

What is the construction of the beta shutter, could it actually be attenuating these borderline gamma?

Date: 2017-06-19 07:22 am (UTC)
From: [personal profile] eub
X-rays I guess because gammas would dose the whole neighborhood more, and maybe betas wouldn't go far enough?

28 KeV photon has an attenuation length of a couple of cm in water, just going by that little Wikipedia graph, so that seems about right for the purpose.

Huh, I didn't realize that betas and alphas don't follow an exponential falloff with penetration. They interact differently, slowing down. That page says betas have a linear falloff in energy (~2 MeV / cm in water), and alphas actually drop a spike of their energy at a certain penetration distance, like cute little depth charges. (If that distance weren't so darn small, alpha could be great for radiation dosing from the outside.)

So 28 KeV X-rays have about the same penetration as about 4 MeV betas. Which is a mondo beta, I'm not sure you get those, though where is a complete list of decay energies?

Date: 2017-06-16 12:43 pm (UTC)
amaebi: (Default)
From: [personal profile] amaebi
That's really interesting.

Date: 2017-06-17 03:43 am (UTC)
basefinder: (Default)
From: [personal profile] basefinder
Will you have your detector with you tomorrow?

Date: 2017-06-17 05:21 am (UTC)
zyzyly: (Default)
From: [personal profile] zyzyly
The scientist/nurse in me wants to encourage you to stick that probe down his pants every week for the next 6 months and see how the readings change over time.

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