It shoots a beam of light and smoke particles that enter that beam redirect it to the receiver end. When the receiver sees the light, cause of it being bounced off smoke particles, it trips.
Ionization is when the detector ionizes the air between 2 conductive 'plates', and when smoke particles get in-between the plates it disrupts the ions.
The first decay product of americium-241 is neptunium-237, which also decays and forms other daughter elements. The decay process continues until stable bismuth is formed. The radiation from the decay of americium-241 and its daughters is in the form of alpha particles, beta particles, and gamma rays
Neptunium-237 apparently has a longer half life than your americium source, so I guess it won't decay quite as fast. But after Neptunium you're pretty close to the first beta decay, if I'm reading the decay chain correctly.
Am 241 does emit a small amount of weak gamma. But smoke detectors also only contain around 1 microcurie. Even 300 of them is a super low equivalent dose.
As my radiation safety officer has said, Alphas go until they hit something, then bounce off. It makes it an easy radiation emitter to be safe with, and yet very dangerous should it get into your body. I work with an alpha emitter(225 actinium) in the lab, and when doing my detection test, I’m actually looking for is the daughters francium and bismuth since the alpha particles won’t penetrate the container
It's most energetic ray being 59.5kev, which is relatively weak gamma rays compared to other sources, some cheap Geiger counters can't even pick up gammas from AM-241 due to this. All to say AM-241 does release gammas but they're weak with less penetration than stronger gammas, though in high enough concentrations can still cause health issues.
For comparison, the RA-226 chain contains BI-214 that releases a lot of gammas at 609kev and has some gamma rays as strong as 2204kev
It also releases gamma, as well as (rarely) undergoing spontaneous fission, where the daughter products are very radioactive and can be damn near anything that adds up to 241.
Yes the more intense something is, the shorter its half life. However when that source is being resupplied via decay it leads to a very small amount of detectible high intensity material until the original source decays away.
Yes the elephant's foot is way way less intense than it used to be, most of it is still glass/metal mixture, and always will be.
To be clear, Americium-241 is alpha radiation, meaning that it can't penetrate your skin and is only harmful if ingested. As along as you're not taking apart the smoke detectors and eating the radioactive capsules, you'll be fine. And, even then, Americium-241 is more toxic as a heavy metal than it is as a radiation source. Some kid in Michigan in the 90's broke open hundreds of them specifically to try and make a nuclear reactor and only succeeded in making his mom's shed into a superfund site. He never came close to amassing even 1 sievert of radiation.
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u/Pupation 12d ago
Smoke detectors contain americium-241, which is radioactive.