I said I was going to make rad techs out of you guys and by gum I meant it!
Several readers want their own Geiger counters. They are fun to play with, for maybe the first dozen hours.
The next few thousand tend to drag a bit, though.
We don’t really call ’em “Geiger counters”. In fact we don’t usually use “Geiger” at all, it’s either “Geiger-Müller” or “GM”.
Older school techs like me call ’em “friskers”. Some techs, like precise ex-Navy types, may say “pancake probe”. That’s more informative becaue “GM” is understood and they’re telling you the exact probe being used. But the pancake probe has been the default for decades.
If there’s a basic rad instrument, this is my choice. Because it’s the most sensitive, it’s useless for dose rates. And it only sees about 1% of gamma rays (the rest pass through without interacting). But if it’s not screaming at you, at a count rate immensely beyond what Hollywood finds threatening, you’re not in a dangerous gamma or x-ray field.
If it is screaming at you, but isn’t pegged past 500,000 counts per minute…you’re still not in a dangerous field. It can’t measure dose rates, but it sure detects them.
Because of that sensitivity. It still boggles me. It’s not merely unsurpassed by any instrument, in any field, at any cost. That sensitivity is inherently unsurpassable.
Because every click of that meter is registering a single quantum event. The ionization of one atom.
In perfect conditions, the human eye can match that. The light-adjusted human eye can detect a single photon. Quite a few different types of rad instruments also match it.
But I don’t think detectors in other fields do. Perhaps hideously expensive lab equipment. But the frisker is a (relatively) cheap field instrument. Are there field chemical detectors that can catch a single molecule? I seriously doubt it.
I’ve used this instrument more than any other, thanks to the drudgery that is “smearing and clearing”. It might eventually be passed by the 1″ by 1″ field NaI (sodium iodide) instrument. That might happen if I stay where volumetric activation is more of a concern than surface contamination. But that prima donna NaI doesn’t see beta radiation at all.
So I declare the lowly GM frisker to be the utility infielder of the radiological world.