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 2.GQ Geiger Muller Counter
 Experiment: High radiation with my 500+
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Marta

Spain
2 Posts

Posted - 04/16/2020 :  01:45:19  Show Profile  Reply with Quote
Hello everyone!
I want to share a very common experiment but with an NOT expected end.


1- Buy an old watch in a garbage market.

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240327 bytes


2- That was the result of my Geiger in his first measurement.

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107212 bytes


3- I decide to disassemble the watch, to avoid that separation that the glass provides.

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248509 bytes


4- Final result of the Radio measurement without any protection.

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90531 bytes


It seems too high to me. What do you think?

Gq GMC-500+
Latitude: 41.221110
Longitude: 1.539394774

Edited by - Marta on 04/16/2020 01:45:53
Reply #1

EmfDev

1245 Posts

Posted - 04/16/2020 :  08:58:41  Show Profile  Reply with Quote
Seems like you got an interesting clock there :D.

How long did you measure the CPM?
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Reply #2

Marta

Spain
2 Posts

Posted - 04/16/2020 :  23:17:05  Show Profile  Reply with Quote
Hello EmfDev

4-5 minutes.

Gq GMC-500+
Latitude: 41.221110
Longitude: 1.539394774

Edited by - Marta on 04/16/2020 23:17:30
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Reply #3

ullix

Germany
492 Posts

Posted - 04/17/2020 :  02:03:40  Show Profile  Reply with Quote
I agree that this high-count is highly suspicious.

Is there anywhere something like a manufacturing year on the clock? Very likely the dials are painted with Radium (they do glow in the dark?). Radium 226 is an alpha-emitter, so you could not detect it in an GMC500, but in its decay chain are multiple beta and gamma emitter, which would produce counts.

This link shows a gamma spectrum https://www.gammaspectacular.com/blue/ra226-spectrum (despite the labelling - it is from the decay chain compounds, not from Ra226 itself).

But the cover glass of the clock (your first picture) would probably have held back most betas, and yet, 1171 CPM is a pretty good clip, not to mention the 11000 with the glass removed.

I suspect some defect in the counter, perhaps a misadjusted voltage, or an electronic defect. Is that a 500 with a dual-tube?

You probably do not have access to a 2nd counter to compare the readings with?

Then I suggest to verify that your counter gives reasonable readings. The only easily accessible and reproducible source for radioactivity is Potassium salt. I have detailed this in my "Potty Training" article (https://sourceforge.net/projects/geigerlog/files/Articles/GeigerLog-Potty%20Training%20for%20Your%20Geiger%20Counter-v1.0.pdf/download ) it includes some advice for what to shop for.

Run a test and post results, please.
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