Tin, and Pewter, and Copper, and Iron, Oh MY!

How to build the perfect shield for your measurements? Discuss it here!
Mike S
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Joined: 25 Apr 2020, 10:24
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Tin, and Pewter, and Copper, and Iron, Oh MY!

Short question: Is pewter (tin alloy with antimony and copper) an acceptable substitute for pure tin for use between copper and lead? Any other good options.

Background:
I'm putting together a basic shield and I'm struggling with choosing and buying the inner portion to reduce lead x-ray.

At first I thought the extra effort to put copper and tin as inner layers under the lead was probably more than I needed at this stage in my hobby. So I built a simple lead-only partial shield and it knocked down the background nicely from 125 CPS to 25 CPS. I thought that would do what I wanted until I saw that the spectrum now had a very large lead x-ray peak. No problem, I'll just buy some copper pipe and some tin sheet and knock this thing out...

First, copper pipe large enough for my detector was quite expensive and not available from a normal hardware store. I did find someone selling one foot lengths on ebay and have a piece on order. MUCH more expensive than I expected, but, well, moving on...

I really got stumped with the tin sheet:

- Tin sheet is very expensive and hard to find.
- I looked into using all copper, zinc, or steel but they have a much thicker HVL and the price starts getting expensive in the thickness I want. Also, the larger the inner shield, the more lead I need to keep the same thickness. If I had access to short cut-off sections of material, steel could be a good way to go, but even a short section of steel pipe with a 3 inch (~7.62 cm)ID with 10mm wall thickness is hard to find, and longer sections get expensive fast.
- I considered buying tin shot because it is much cheaper than tin sheet. My thought was to 3D print a cylindrical container that would hold the tin shot. But tin shot tends to be large enough that I'd have to have a large volume to assure it could pack efficiently and have sufficient effective thickness (back to more and more lead, plus it's not that much cheaper).

I have seen posts where folks talk about using pewter, which has significant antimony and a little copper (usually?). Does the antimony cause any issues? Is this really what people are using, and not purer tin? Pewter is still expensive (it's still mostly tin), but at least there's a few more purchasing options (Contenti is the best option I've found so far).

If there's a better source, method, or material, please let me know. Otherwise, I'll brace myself and move forward.

Mike S.
Mike Sullivan
Central Coast of California, USA

sgt_bear
Posts: 110
Joined: 16 Jan 2017, 07:06
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Re: Tin, and Pewter, and Copper, and Iron, Oh MY!

What do you consider expensive?
I've used a ~50mm copper tube for my shield, and added 4 sheets of tin (320x200x0.5mm). The sheets were 30£ in total. 2mm tin is enough for shielding pretty good.

I got the sheets from pewtersheet.co.uk
- Jonathan from Switzerland

Mike S
Posts: 80
Joined: 25 Apr 2020, 10:24
Contact:

Re: Tin, and Pewter, and Copper, and Iron, Oh MY!

For reference, I've only spent $20 USD on lead at this point, so I'm still adjusting to the cost ratio for the inner layers. The pure tin solutions I've found so far are$120 USD or more.

Mike L
Michael Loughlin

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