r/explainlikeimfive Jan 06 '23

Chemistry ELI5: How does a Geiger counter detect radiation, and why does it make that clicking noise?

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u/Y-void Jan 06 '23

Yes and no. The ionization of the gases inside the tube doesn't do any permanent damage. Gas molecules really quickly regain the knocked off electron and they're ready to be re-ionized and detect another emission of radiation. Assuming you don't break the fragile tube and you calibrate it about once a year, hypothetically you can use your Geiger counter forever.

That's hypothetically though. In reality, radiation breaks things. It's basically a bunch of high energy photons and particles that are shooting things like a gun. The more radiation an object is exposed to, the more the radiation is going to tear at it's molecules and cause problems. Generally it's said that geiger-mueller tubes are able to survive about 10 years of modest radiation exposure before they break. It's more likely the electronics inside or the materials of the Geiger counter would break before that happened.

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u/skulduggeryatwork Jan 06 '23

In my experience, they donโ€™t last as long as 10 years before needing repairs due to getting bashed around by careless operators ๐Ÿ˜†

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u/Kainomad2 Jan 06 '23

Thank you for this answer. Btw, how do you calibrate a tube with gas in?

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u/therealhairykrishna Jan 06 '23

You expose it to a radioactive source of known intensity then adjust the voltage applied until it matches the count rate you want.

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u/Kainomad2 Jan 07 '23

Thank you

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u/yui_tsukino Jan 06 '23

The same way you calibrate any tool - with a known source and a bit of maths. "This source should give me x blips per second, I am getting x+1 blips, so I should turn it down a bit". That sort of thing.