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Petrovski
Netherlands
16 Posts |
 Posted - 04/06/2016 : 09:42:17
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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:
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73775 bytes
Check source details:
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132219 bytes
Check source location (on top of the survey meter):
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80834 bytes
Measurement with the Victoreen (set to CPM):
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87105 bytes
Measurement with the GMC-320 Plus:
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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
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| Reply #1
Distelzombie
Germany
202 Posts |
Posted - 04/07/2016 : 03:49:56
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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
Petrovski
Netherlands
16 Posts |
Posted - 04/07/2016 : 10:22:04
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| Good point. The plastic does block most of the GM tube. Will try. |
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| Reply #3
Setagaya-Observer
7 Posts |
Posted - 04/11/2016 : 01:54:51
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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.
Source; https://www.orau.org/ptp/collection/civildefense/checksources.htm
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;
https://www.elimpex.com/products/survey-meter/victoreenprobes1.pdf |
Edited by - Setagaya-Observer on 04/11/2016 02:06:01 |
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GMC-320 Plus vs Victoreen 190 survey meter
