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 Advice for Geiger counter for fossils and minerals

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i80386 Posted - 12/06/2018 : 12:42:40
Hello everyone! I need advice on which model Geiger counter is suitable for me. I am interested in collecting fossils and minerals. I know that some of them may have accumulated somewhat radioactive substances from soil and water and I would like to avoid such specimens. My question is a model like GMC-300E or 320E plus whether it's sensitive enough for such measurements, or do I need something to take into account alpha radiation like GMC-600 PLUS?
13   L A T E S T    R E P L I E S    (Newest First)
ullix Posted - 01/09/2019 : 04:47:47
ok, seems that all is lining up.

The KCl amount is really on the low side. The fact that you did get an increased count rate suggests that you did the measurement well!

I recommend to use at least 1 pound of reasonably pure KCl in a bag positioned below the counter, and if you can, another pound above the counter. With the back-plate removed if you aim for high counts.

The reason is that even betas pass through - my guess - a millimeter of KCl, and the rather high energy gammas easily pass through centimeters of KCl and the whole counter. Therefore from a pound of KCl spread over an area the size of the counter, most of the betas will be absorbed in the KCl and the counter, but most of the gammas do come through.

i80386 Posted - 01/08/2019 : 09:07:10
Hello, I also think it is a high background, the official data for my city is an average of 0.14 ÁSv/h. My apartment is build with concrete and bricks, perhaps it contributes to the higher background - 26.5 cpm (0.172 ÁSv/h). At the place, where I work, the average value is 22 CPM (0.143 ÁSv/h) - matches the official data. In the Potassium Chloride test, I used a small amount of salt - about 5 tablespoons in a dish covered with foil and a GMC 320+ placed on it without a lid. Maybe this explains the lower score - 80 cpm. Also, potassium chloride is mixed with 33% sodium chloride.
ullix Posted - 01/08/2019 : 01:51:01
Well, the difference between 26 and 33 CPM isn't that much, and given you have measured for only 30min, what makes you believe there is even a difference, when you consider statistics?

Remember, the StdDev is square-root of CPM, so the distributions already overlap significantly. Now you need to reduce the Std.Error by measuring long enough so you can decide whether these two distributions are different. It is a bit of a challenge, see my Going Banana article on a similar question for how to proceed https://sourceforge.net/projects/geigerlog/files/Articles/GeigerLog-Going%20Banana-v1.0.pdf/download

Your counter responded to the KCl sample in the expected fashion, though a bit on the low side. The response to the fossil tooth was similar, though even lower. I think it is possible that teeth in general have elevated levels of Potassium (need to be verified) which might explain the slightly elevated level (if true) over background.

Though calling that "radioactive" is a bit of a stretch.

The background is a bit on the high side compared to many other measurements. Is that confirmed by some official measuremnts on nearby sites?

i80386 Posted - 01/05/2019 : 07:44:43
Thanks, I will try a new installation following the instructions in the manual. In the meantime, I made 30-minute measurements with GQ Geiger Counter Data Logger Pro demo. I did a test with potassium chloride 70% and I got the results with an average 35 CPM with back cover, and 80 CPM without cover.
One of my fossils - a 5 cm mosasaurus tooth from Morocco (probably from a phosphate mine) is also slightly radioactive - about 33 CPM with a cover and 45 CPM without cover. In all tests without cover the counter was in a thin plastic bag to avoid contamination. For comparison, the background here is an average of 26.5 CPM.
ikerrg Posted - 12/25/2018 : 10:54:59
It seems that you have not installed the required Python modules (like serial). Read the manual as ullix says, it is everything there.
ullix Posted - 12/23/2018 : 03:08:34
It may be a horrifying thought, but you may have to look into the manual for installation instructions.

And follow them!
i80386 Posted - 12/22/2018 : 11:19:01
Hello, Ullix! I already have GMC-320+ V4 and I'm trying to make my first measurements. I downloaded the latest version of Geigerlog - geigerlog-scripts-v0.9.08b-rc3, and then following the instructions, I downloaded and installed Python 3.7. And then I can not run Geigerlog. I have no experience with Python-based applications and I can not start anything. I have copied the Geigerlog folder to the root directory C: What exactly command should I write in the Windows command prompt or maybe in Python IDLE to run the software?

EDIT: From another discussion I saw you recommend
python c: \ geigerlog \ geigerlog -d from the Windows command prompt, but it causes me the following error:

C: \ Users \ user> Python c: \ geigerlog \ geigerlog -d
Traceback (most recent call last):
File "c: \ geigerlog \ geigerlog", line 62, in <module>
import serial # interface to USB-to-serial
ModuleNotFoundError: No module named 'serial'
The USB driver has been successfully installed and the device successfully connects to the GQ Geiger Counter Data Viewer Re. 2.56 (at COM45). OS is WIN7 64bit
ullix Posted - 12/08/2018 : 05:13:12
Yes, alpha emitters should be treated with proper precaution. If the compound could shed dust or fibers, that do or may contain the alpha emitters, I'd keep the compound under wraps. E.g., old gas mantles are a convenient source for Thorium (emitting alpha, beta, gamma). I always keep the gas mantles in a plastic pouch and never take them out. The alphas won't pass the thin plastic foil, but this is not the main concern; it rather is the release of fibers from the gas mantle material. Such fibers itself may be a lung health concern already, topped with them also carrying the Th.

I don't know how you preserve fossils. Perhaps those exhibiting radioactivity could be covered with a lacquer finish? Or simply put in a fitting plastic bag/pouch/container? At least better than throwing away perhaps valuable fossils.

See the "decay chain" topic, nicely done in Wikipedia https://en.wikipedia.org/wiki/Decay_chain , to understand what radioactive substances might be found in fossils (if there are any at all). Look e.g. into the "Uranium Series", and find Ra226. It is shown as a 100%-alpha-emitter, no gamma. But when you look at the gamma spectrum of Ra226, you see this:

Image Insert:

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A rather complex gamma spectrum, mainly resulting from gammas emitted from daughter nuclei in the decay chain of Ra226. Unfortunately, Wikipedia says nothing about gamma emission, but in all decay chains you will find alpha, beta and gamma simultaneously.

Note that this "alpha-only" Ra226 is actually used to calibrate gamma-response of Geiger tubes, see GeigerLog manual, chapter "Appendix G - calibration".

The GMC-500+ (the plus-version) has dual tubes, and many issues, reported in this forum. See e.g. here http://www.gqelectronicsllc.com/forum/topic.asp?TOPIC_ID=5369 I'd strongly recommend against it for your purposes (the 2nd tube is MUCH less sensitive, so no help at all).

The GMC-500 (the non-plus-version) and the 300 and 320 series are functionally equivalent; they all have only a single tube, always a M4011. The memory is big enough even in the 64k-only in the 300E+; I don't see WiFi, as it is implemented, an advantage. While the 3xx series clock is notoriously off, the 500 has a more precise real-time-clock. However, in my unit this clock broke right away, and so I can't make any history recording in the 500, while it at least works with the 300, although the timing is off.

The one clear advantage of the 500 is the bigger display of 128x64 versus 128x32, and operating the buttons a bit smoother. This is worth considering for convenience and handling.

i80386 Posted - 12/08/2018 : 01:25:53
Thanks, Ullix ! Very useful information and software (GeigerLog) that I can use when I buy a compatible device. My concern about alpha radiation is because I read that it is particularly dangerous when inhaled and swallowed dust, and it is difficult to detect. If there really is no source in the nature that emit only alpha particles, beta devices like 300 / 320E should handle the measurement. I have one more question, the GMC-500 is only a bit more expensive, is there any benefit to my type of measurement, or its second tube is an advantage for strong sources of radiation? The GMC-600 + comes out of my budget, especially with the delivery to Europe.
ullix Posted - 12/07/2018 : 10:36:46
Thanks for the interesting links. It reminded me of the way wood is petrified, and since I had once bought a good sized chunk of it in Petrified Forest, Arizona, USA, I tried it right away with my counters using GeigerLog.

Image Insert:

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The blue trace is from an GMC-300E+ counter with GQ's default M4011 tube, the light-brown trace from an RadMon+ counter with an SBM20 tube (a Russian standard tube).

Even without running the stat numbers you can see that the rock does not deliver any extra counts - just the same as BG (background), and basically the same for both tubes.
So, no success with my Rock :-( but I liked the idea.

For your fossils it depends what you want to show. As you seem to want to eliminate those with too much radioactivity, your criterion looks like safety. However, background levels of ~16CPM as in my experiment are far, far below any unsafe levels.

For example, while background at my location in Northern Germany is 20 CPM (rounded up), the level you get in an aircraft cabin at cruising altitude 30000 ft due to cosmic radiation is more than 10 times that much (depending on latitude, at my location it is about 300CPM, measured with a 300E+ counter. Do you consider flying dangerous due to cosmic radiation? If not you have a established what levels you are willing to tolerate, and should apply this for radiation from fossils as well.

Thus the simplest of all counters will suffice for your task!

However, if you criterion is more to compare fossils that have almost none with those that have a weeny little bit of radioactivity (any living organism needs Kalium; so this simply must be present!) you can to this with a simple counter as well, but it needs loooong recording times, probabyl at least multiple days (D A Y S). As an example, see my Going Banana article (https://sourceforge.net/projects/geigerlog/files/GeigerLog-Going%20Banana-v1.0.pdf/download ) where I did to bananas (to determine the K40 in them) what you would have to do to your fossils.

While it can be done with a M4011 tube, you'd be better off with a much bigger tube, like the pancake tube in a 600+ counter. Whether this is worth the extra cost is up to you to decide.

In any case, you will need long counting times and software to support that with graphics and statistics. In other words, only GeigerLog will do :-))
i80386 Posted - 12/07/2018 : 06:43:19
Thanks emfdev and ullix! I found information about the radiation in some fossils in discussions like these: h**p://blog.hmns.org/2018/03/why-dinosaur-fossils-are-radioactive-sometimes/
h**p://www.thefossilforum.com/index.php?/topic/27972-radioactive-fossils/
As far as I understand, uranium is most commonly found, as well as some other natural radioactive elements that replace the fossil matter in the fossilization process.Their concentration is usually even higher than in the environment. If, indeed, those who emit alpha at the same time emit beta and gamma, maybe I can find them (even these with low activity)with a device like a gmc-300e plus? What is the cumulative measurement method?
ullix Posted - 12/07/2018 : 04:19:14
Doesn't it seem a bit illogic to consider buying a specially sensitive counter to detect activity so low, that you can't detect it otherwise?

Given the omnipresence of natural K40 (Potassium) you will detect this (beta, gamma). For more details on K40 see Potty Training (https://sourceforge.net/projects/geigerlog/files/GeigerLog-Potty%20Training%20for%20Your%20Geiger%20Counter-v1.0.pdf/download )

If you detect "something" - how do you determine that it is not from K40? If you can't you would needlessly discard your whole collection!

What is it that you suppose is added from "soil and water"?

Further, I am not aware of any naturally occurring alpha emitter, that is not also an emitter for gamma and beta. In fact, it is not trivial to verify alpha emittance. How would you do that and what specific additional info does that give you more than any of the other counters?
EmfDev Posted - 12/06/2018 : 16:12:25
Hi i80386,
We recommend 600+. 300/320+ can be used but you need to use cumulative counts to check for activity. 600+ is more sensitive than 300/320+.

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