I made a shield from junk. It seems to be pretty effective, so I'm not too ashamed to share it. The detector portion of the shield is built around a 12mm thick tungsten tube. I camped the tube into the middle of a large soup can and then filled the can with lead. This produced a 24mm ring of lead around the tungsten. For the base, I made a mold out of scrap wood. The bottom of the mold would be the top of the base, giving a nice flat surface to work with. The interior of the base was borrowed from John Bell's shield write up. I used 2mm pewter sheet and 22 gauge copper, cut to size on a scroll saw. After all the pieces were cut, the edges were cleaned up on my flat lap.
With my 1 inch NaI (Tl) high sensitivity detector at 400VDC, background is 1.12 counts per second. Some ugly napkin math shows that my shield should be around 4 half value layers for 226Ra. A quick test spectrum of 133Ba showed a prominent Cs x-ray peak, but hardly any peak from lead.
Here is the detector shield
Casting the base
Freed from the mold, a bit of trimming to do
Cutting pewter on the scroll saw
Here is the fitted inner shield. The inner cavity of the base was a little rough from casting, the wood I used burned away more than I expected.
Here is the lid with detector window
Looking down into the base
All of the lead was covered with aluminum tape to keep any dust contained.
Finished my junk shield
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Geoff
- Posts: 141
- Joined: 01 May 2015, 12:21
Finished my junk shield
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Last edited by Geoff on 27 Oct 2017, 18:04, edited 1 time in total.
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keuleeule
- Posts: 76
- Joined: 31 Oct 2016, 09:09
Re: Finished my junk shield
Hi, Geoff,
Any hints where to get a tungsten tube ?
And the pewter, that is already in boards ? What kind of searchword should we use ?
Regards kolja
Any hints where to get a tungsten tube ?
And the pewter, that is already in boards ? What kind of searchword should we use ?
Regards kolja
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Geoff
- Posts: 141
- Joined: 01 May 2015, 12:21
Re: Finished my junk shield
The tungsten was obtained while I was working as a radiation protection technologist in the oilfield. I'm not sure where one could find one. The pewter sheet was obtained from Contenti at https://contenti.com/metal-n-metal-clay ... heet-metal
