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 2.GQ Geiger Muller Counter
 Soft X-Rays
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David VanHorn

USA
3 Posts

Posted - 03/14/2018 :  08:43:36  Show Profile  Reply with Quote
Using the GMC-320+

I am looking for suggestions for shielding against soft X rays, 50kEV and lower. I would prefer to use thicker materials so that it is easier to get the thickness right.

Additionally, anything I can do to "prove" that what I am seeing is indeed X-Rays and not something else.

Ideas?

Reply #1

GBG12

Canada
48 Posts

Posted - 03/15/2018 :  19:09:33  Show Profile  Reply with Quote
Lead seems to be the go-to shielding material in general, but I don't know if there is anything that is particularly better at shielding lower energy X-rays vs. higher. The greater basic penetrating power of higher energy might be enough for your purposes. There are materials that stop higher energy X-rays better than lower ones compared to Lead , such as concrete and steel (see https://nvlpubs.nist.gov/nistpubs/jres/38/jresv38n6p665_A1b.pdf).

Edited by - GBG12 on 03/15/2018 19:11:07
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Reply #2

ullix

Germany
346 Posts

Posted - 03/18/2018 :  08:19:38  Show Profile  Reply with Quote
I can't imagine that you can "prove" what you want based on partial absorption, unless you have a high intensity source of soft X-rays.

50keV is in realm of medical Xray machines, and 50keV is only a little bit more of what you got from the old big, color-TV tubes, I believe there voltage was about 30kV. To capture the xrays in those days they made the front glass a little bit thicker and put more lead into the glass formula. Was it 1cm thick? If so, for the equal effect on 50keV you might need 2cm glass. But you would have to determine whether you want a 90%, 99%, or 99.9999% reduction. I don't know what the TV glass yielded. Glass of that thickness is not easy to handle anyway.

Plastic is easier. But with glass being mostly Silicon, and plastic mostly Carbon, with a lower Z, you would need even thicker plastic.

Lead has the strongest effect for a given thickness. But there is a catch: if you have beta source around - and anything stone has potassium - you might get Bremsstrahlung. Depending on the intensities of your source of interest and environment, you could obscure your signal.

I am discussing some aspects of this in my Potty Trainging...Appendix (here: https://sourceforge.net/projects/geigerlog/files/GeigerLog-Potty%20Training%20for%20Your%20Geiger%20Counter-v1.0.pdf/download)

Can you provide more details on what you are trying to prove?
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