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
Finished my junk shield
Last edited by Geoff on 27 Oct 2017, 18:04, edited 1 time in total.
Geoff Van Horn
Anchorage and Deadhorse Alaska
Anchorage and Deadhorse Alaska
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
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
Geoff Van Horn
Anchorage and Deadhorse Alaska
Anchorage and Deadhorse Alaska
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