this post was submitted on 02 Nov 2023
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So, in the fine tradition of using bananas for scale...
Bananas are slightly more radioactive than the background, due to potassium-40 content. So an informal unit of radiation measure in educational settings is the 'banana-equivalent-dose', which is about 0.1 microsieverts.
My particle spectrometer saw first light today, and I figure that I could use a banana to calibrate it. Then I noticed that K-40 undergoes a rare (0.001%) decay to 40Ar, emitting a positron. So not only is a banana a decent around-the-house radioisotope source, it's also an antimatter source.
Truly a remarkable and versatile fruit.
Sorry, I understood that.
banned
Nice -- you wouldn't happen to have any ideas on how to differentiate positron annihilation, from the continuous distribution of Ξ²β energies caused by the more common decay mode, using only a PIN photodiode? I'm a bit stumped on this point and suspect it's not possible. I probably need to do gamma spectroscopy but would really rather not.
Reverse the polarity of the bussard collectors and push the antimatter from the warp core into space. Collect this with a big test tube.
the trickery is to detect two gammas emitted simultaneously in exactly opposite directions
Yeah, that's going to be too hard. I only have two SiPMs (besides the current detector) and they are expensive. I figured I could maybe rely on the gamma from the annihilation energy being a quite different energy than the gammas from the more common electron-capture.
However you raise a good point that that would not be a very good demonstration of positron annihilation at all -- just evidence that it's not the other 2 decay modes (and it would take ages to collect that evidence besides). Ah well. Got plenty of other science I can do instead.
Probably I'll tackle something easier like checking for radon decay products in petrol.
that's how real commercial PET scanners work, so it's not too hard to make it work
'Not too hard' is a bit of a spectrum I guess ;)
I mean yeah, in principle I could cram textbooks for a few months (I know EE and SE pretty well, but particle physics only very basic stuff), order parts made at the factories I know, and would probably succeed eventually. More realistically I'd have to hire a university prof as a consultant to save time.
What I am really unable to construct is a powerpoint presentation that justifies that expense and labor to management :P
Especially in a cost-driven market (my company is in Vietnam). Often the parts for these things are export-controlled too, that can be a real pain. I've gotten irate phone calls from the US DoD before over fairly innocent parts orders -- it's not super fun. I recall it was some generic diode, I must have stumbled on something with a military application I wasn't aware of. The compliance paperwork ended up costing me hundreds of dollars for 20$ in parts, too.
Anyway, if it was something I could just tack on to ongoing research projects, I could maybe get away with it as a marketing expense. It's for a STEM program. It's hard enough to convince management to take the risk on a nuclear & quantum module as-is! I can mostly get away with it because the locally-manufactured beta-detectors cost like 20$ per classroom.
This is some seriously dangerous information to be feeding me bro.
Now.. to find magnets able to contain the antimatter...
Bananas are not typically very high on the danger scale except in exotic (and universally embarrassing) circumstances.
In fact, that's another thing we could use bananas for scale with. Probably driving to work is equivalent to several kilobananas worth of danger daily :)
Anyway, I think the positron should be about 44keV if that helps you calibrate your magnets. The typical banana should produce something on the order of a positron every 10 seconds (although I used much rounding for the sake of brevity). Most commercial positron sources e.g. used in hospital PET scanners, are many times stronger than that!
As someone who tried to push a banana up their ass in uni - it doesn't work.
I/O error.
I understood the joy.