Shielding for ground testing

How to build the perfect shield for your measurements? Discuss it here!
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hurston
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Shielding for ground testing

Post by hurston » 27 Feb 2017, 08:27

I'm a bit of a beginner with all of this. I'm getting a friend of mine to weld me a frame to carry around my (GS-2020) scintillator to take measurements of the ground. I'm going with lead and copper shielding, as seems to be common reading this board, but I'm unsure of the best orientation for the scintillator. Should I have it horizontal, with the length of the canister open to the ground and slightly open at the back for the cable, or vertical with the end down, open to the ground with a hole at the top for the cable? Which setup would give the least noise?

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iRad
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Re: Shielding for ground testing

Post by iRad » 27 Feb 2017, 08:51

Are you sure there would be worthwhile benefit, carrying around the extra weight of a decent shield for normal exploration. It might be easier just to subtract background and wait to you got any samples into a "lab" environment to use the shielding. Dragging around a heavy lead weight can get old real fast.
Best orientation geometry often depends much on the detector itself, and what you are searching for. If the crystal in your detector is more or less balanced in length and width (and the crystal is very good), it may not matter much. But if the length is much longer or shorter than the width, or the crystal has some damaged on one side or another, then orientation could make a larger difference. Cheers, Tom
Please check out my eBay Store: http://stores.ebay.com/The-Rad-Lab
Cheers, Tom Hall

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Steven Sesselmann
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Re: Shielding for ground testing

Post by Steven Sesselmann » 27 Feb 2017, 11:06

Hurston,

The GS-2020 has a 2x2" crystal, so it is not particularly directional. but it might be more convenient to make a cylindrical shield and hold it upright. I think a 3" copper pipe will fit the detector and leave a bit of space for some foam to protect the detector. Wrapping some lead around the bottom 3-4 inches will cut out a lot of the low energy x-rays. Adding more lead gives you a diminishing return. Suggest mounting the detector 1-2 inches from the bottom of the tube, this will give some collimation and also protect the detector.
Steven Sesselmann | Sydney | Australia | gammaspectacular.com | groundpotential.org | rephopper.com | beejewel.com.au |

hurston
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Re: Shielding for ground testing

Post by hurston » 28 Feb 2017, 05:29

Thanks guys, the design is solidifying in my head now.

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