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 2.GQ Geiger Muller Counter
 GMC-320 Plus vs Victoreen 190 survey meter
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14 Posts

Posted - 04/06/2016 :  09:42:17  Show Profile  Reply with Quote
Today I decided to do a quick measurement of the check source of a Victoreen 190 (which I have available at work) with both the Victoreen itself and my new GMC-320 Plus. The Victoreen is professionally calibrated every year.

The Victoreen 190 with pancake probe:
Image Insert:

73775 bytes

Check source details:
Image Insert:

132219 bytes

Check source location (on top of the survey meter):
Image Insert:

80834 bytes

Measurement with the Victoreen (set to CPM):
Image Insert:

87105 bytes

Measurement with the GMC-320 Plus:
Image Insert:

88316 bytes

I only measured for a couple of minutes, but you can clearly see the Victoreen registers roughly 4 times the amount of counts than the 320 Plus. Since the check source is a Cs-137 source which emits beta radiation of 0.5 and 1.1 MeV + gamma radiation of 0.6 MeV (emitted by the decay of Ba-137) and all these radiation types & energies are well within the detection range of the M4011 GM tube, I imagine the difference is mostly caused by the fact the pancake probe has a larger surface and is more sensitive than the M4011 tube of the 320 Plus. And of course, the Victoreen is about 15 times more expensive. It only needs a few seconds to stabilize at ~1500 CPM.

Anyway, just a 'fun' comparison. In the near future I'll do some measurements of a Cobalt 60 source and also compare the 320 Plus with a Berthold contamination monitor.

Edited by - Petrovski on 04/06/2016 09:52:44
Reply #1


193 Posts

Posted - 04/07/2016 :  03:49:56  Show Profile  Reply with Quote
Not exactly.
Try the same again but this time open the case of the 320. The plastic is so thick it blocks much of low power beta radiation.

GMC-300E+ V4.20 with sbt-11a alpha tube

My statements are "stuff-a-hobbyist-says" and not in any way professional.
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Reply #2


14 Posts

Posted - 04/07/2016 :  10:22:04  Show Profile  Reply with Quote
Good point. The plastic does block most of the GM tube. Will try.
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Reply #3


7 Posts

Posted - 04/11/2016 :  01:54:51  Show Profile  Reply with Quote

Radium D and Radium E

Radium D and radium E are the historical names that Ernest Rutherford used for lead-210 (Ra D) which has a 22 year half-life, and bismuth-210 (Ra E) which has a 5 day half-life. Since lead-210 and bismuth-210 are always accompanied by polonium-210, which Rutherford called radium F, such a source is almost always described as Ra DEF. It is possible that the manuals only refer to Ra D and E because the alpha particles emitted by the Ra F cannot be detected by the probe. On the other hand, the beta particles from RaD could not be detected either because they are of too low an energy. A Ra DEF source emits two beta particles for every alpha particle. In addition to the beta and alpha particles, the Ra DEF source also emits a 46 keV gamma ray in 4% of its decays.


I hope this is answering your curiosity.

Regards, your Instrument from Work is a nice one!

Edit; i made a mistake regarding your Test Source, sumimasen o kudasai, here is the correct Info;

Edited by - Setagaya-Observer on 04/11/2016 02:06:01
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