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Posted: 31 Jul 2016, 12:14
I had a request from a customer who wanted me to make shielding for a 2" detector, so I came up with this design made from PVC pipes. The objective here is to make something light that can be shipped to the customer and filled up with lead shot locally.
This design is an improvement on my last design because the detector is shielded on three sides. When the tube is filled with lead shot, and turned around the right way, the lead will surround the sample chamber and the detector. The user may optionally install a lead plug to get full shielding. The disadvantage is the size of the sample chamber is 80 mm Diameter.
Easy enough to make for someone with a few hand tools and a few hours to spare.
Posted: 31 Jul 2016, 12:41
Very nice work and design, thanks for sharing Steve! After careful filling, having the lead encased in PVC has the added benefit of keeping additional contact with it to a minimum. This design is a lot safer and easier than making molds and melting lead. Don't ask how I know this... :)
Posted: 29 May 2019, 16:13
I made a couple of GS-STANDUP's today and added a few improvements. Amazing what a bit of practice does, they come out looking better.
If I was living in the middle ages I would probably have been a tin smith, but now you can just call me the Wizard of Oz :D
So instead of fitting a copper lining inside the detector housing I add it to the elbow before assembling the enclosure, this makes more sense as we end up with less gaps.
This could have been a tricky shape to cut, but I remembered a trick my old man taught me. I first bandaged the plastic elbow tightly with several layers of masking tape, then I used a box knife to cut the tape along the joints before carefully peeling the tape off and flattening it to a piece of paper. This gave me a pattern with the right shape to cut the copper.
The copper sheet is 0.8 mm rolled copper, so I traced the patterns onto the copper, cut out the pieces with some tin snips and used a blowtorch to anneal the copper, making it easier to bend.
With copper sheet fitted and soldered together in the joints, I repeated the pattern making process for the outer skin of tin. (slightly larger pattern).
I had to source the pewter sheets from the UK, as there were no local suppliers here. Followed the same process and in the end used a big soldering iron to weld the joints.
Finally the elbow is glued into the enclosure and then the whole thing is given a coat of paint.
I also made a 3D Cad drawing for a plug, but I don't have a 3D printer to try it. If someone has a printer I can post the stl file. The plug is hollow and can be filled with led shot.
Posted: 30 May 2019, 01:08
WOW. That shielding is beautiful and exactly what is needed to reduce x-ray signals from the lead in the STANDUP without reducing it from the sample. My solution wasn't as pretty as that though how I cut the shapes was less calculation and more trickery as well.
This is the shielding I had installed so Pb-210 in samples could be measured.
Posted: 30 May 2019, 01:15
Steve: I have access to a part printer (and have already begun printing fun parts for my STANDUP-20 for gamma spectroscopy). Please message me privately and I can see if it's something I can make. (I can't get the private message thing to work for me for some reason today.)
Posted: 20 Jun 2019, 16:18
Here is what the slightly modified plug looks like when printed (sorry for the poor photography).
The great news is that Steve's design works fantastic in the GS-STANDUP-20!
I've had some additional custom sample holders printed for my aluminum plug (that have had to go back to the drawing board due to the "dimension drift" and as a result of how I added extra shielding to my GS-STANDUP) that have resulted in some design improvements to printed plugs that will make them easier to shield. I'll share these designs when they are built and tested.
Printing parts isn't like machining parts from metals or bulk plastics. After printing it is advisable to heat each piece to "anneal" it resulting in a stronger part; however, depending on the material or how it was designed and printed, this often results in slight changes in dimensions. Printed parts also absorb water from the atmosphere during production depending on the additives present in the plastics (which also can slightly change final dimensions). In this effort the only difference between the black and white "cups" is an additive that makes one of those PLA parts black. The "lid" is made from a plastic that contains carbon fiber that results in a surface nice enough to place text and markings that is relatively strong. The white cup can be assembled and disassembled with some effort (and may require glue once the lead shot is in place) but if the black cup is used it will likely be a near-permanent installation due to slight dimension differences though both were printed from the same file.
Posted: 20 Jun 2019, 16:55
Forum has been active lately so you might have missed this post https://www.gammaspectacular.com/phpBB3 ... f=21&t=525
As you can see I couldn't resist the temptation ;)
Posted: 21 Jun 2019, 02:40
Thanks for letting me know. (The post was made during a time I was on a cruise in the Arctic Ocean with no internet access; being the first vacation I've taken since 2003 I didn't see it.) I hope you have a great time with your new toy and get some fantastic parts for your efforts. PLEASE be warned that not all epoxy glues are chemically compatible with printed parts when encasing lead in shielded plugs! (I had a very bad experience with dye-impregnated epoxy and printed sample holders.) One way of getting around it was to coat the printed part with a couple of layers of clear fingernail polish before using the epoxy to encase the sample.
Posted: 21 Jun 2019, 07:24
Yes I agree, when you have too much fun working you never get a holiday, I think 2003 was the last time I had a vacation too :)