Tools of the trade, Number 1–The frisker.

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.

About wormme

I've accepted that all of you are socially superior to me. But no pretending that any of you are rational.
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11 Responses to Tools of the trade, Number 1–The frisker.

  1. Mountainbear says:

    I’d very much enjoy scaring people with it. Especially my parents’ neighbors.

    • wormme says:

      I put a scare in a roommate once, after he told me he was getting a medical uptake. I brought by a microRem meter with audio, and started advancing toward him from about 30′ away. Eyes can’t get bigger than his did.

      People can get a decade’s worth of radiation from one of those, in a matter of days. And to date, I’m unaware of any heightened incidence of cancer among recepients of diagnostic uptakes.

  2. Leopold says:

    Believe it or not, I asked my girlfriend to get me a CD V-700M for last Christmas. Budget got in the way, but my birthday is coming up (it will be that or a Pappenheim model sword/rapier w/ a live blade — yeah, I’m weird). Thoughts on the CD V-700M? I figure I want to be able to at least detect alphas and betas, as contamination is much more likely to be an issue than involuntarily snacking on gammas, and I can do the mental arithmetic to convert counts to dosage just fine.

    Realistically, it will be for noodling around and playing with rocks (girlfriend studied geology). I got her vaseline glass jewelry (19th century, so non-depleted Uranium) both because it looked really beautiful and so I’d have something other than bananas to point at. 🙂

    http://www.radmeters4u.com/more.htm

    • wormme says:

      Victoreens! Man, does that take me back. I saw a GM kit for ~$195 this week, somewhere.

      You’ve got some of the hotter items still around. The old red FiestaWare is hard to top, though.

      On eBay I saw someone hawking “the Godzilla!” of uranium samples, claimed to be reading 100 mR ( 1 mGy) on contact. That was pre-9/11. The free-wheeling market dried up a lot after that.

  3. Mike says:

    Thanks for keeping me informed.

    You’re an island of sanity, and have helped me evaluate what I read elsewhere.

    Get some rest. You have earned it.

    I found you through two bloggers I admire – JonahNRO and Rand Simberg.

    Mike
    Merritt Island, FL.

  4. gene says:

    Heh. About a month ago, I bought a pack of 6 CD V-742 Dosimeters and a recharge unit.

    Since it measures Roentgens, I’m not expecting any circumstances to use it, thankfully.

    • wormme says:

      We always keep “pencil dosimeters” around, but I haven’t used one in a while. And once, at an electron accelerator, those were the only things that could give us any idea of a very specific radiological condition.

  5. RKM says:

    Interesting site! AoSHQ directed my attention here. Thanks for the info posted.
    I was wanting to get rad detector a while back and was looking at the Ludlum Model 3 with the 44-9 pancake probe. I became interested in getting one after reading about the Co-60 contaminated steel that came in from Mexico a few years back. It was only detected after the truck driver made a wrong turn and passed the gate of the LASL in Los Alamos, NM and set off the detectors. At any rate, I blew off getting one at the time and now wish I had bought one before the latest hysteria, re: Fukashima I’m more wary of undetected radiological incidents arising from negligence and ignorance (such as the above mentioned incident) than anything.

  6. Pingback: Oops! Sorry crosspatch and BlakeBlake. | World's Only Rational Man

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