New Shield

How to build the perfect shield for your measurements? Discuss it here!
wraith_oz
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Re: New Shield

Post by wraith_oz » 27 Mar 2017, 09:02

I would have made a round shield but couldn't find anything suitable to use as molds to form the lead. The melting point of lead free pewter is less than that of lead hence you can't use a pewter tube as a mold unfortunately.

Make sure that the shield you make is large enough for a Marinelli beaker if you are interested in measuring very low levels. Mine isn't.
John Bell from Central Victoria (Australia)

Setup: GS2812 detector/GS-1100 Pro interface; E-MU204 adc; lead (30mm) shield/ 2.0mm lead-free pewter/0.51mm Cu liners

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Peter-1
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Re: New Shield

Post by Peter-1 » 30 Mar 2017, 02:25

Hello John,

Unfortunately I do not get a tin. I have but still sufficient molybdenum. Can I use between lead and copper this molybdenum?

Thank you
Peter

Martin4s
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Re: New Shield

Post by Martin4s » 05 Apr 2017, 18:06

All parts are nearly in. I wanted to smelt some batteries. However knowing lead oxide is a bad thing to throw somewhere. I decided to get some refined off of ebay. 150 Lbs. The AGM Batteries will go to be recycled properly. You still should wear a mask once melted;-)

Martin4s
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Re: New Shield

Post by Martin4s » 05 Apr 2017, 18:17

Good Enough. It is important to discriminate the wave. According to back Ground.

Boris
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Re: New Shield

Post by Boris » 07 Apr 2017, 04:35

Hi all,

OK, did manage to stumble on a pile of tin plates and cups, for 20 euro's....
and it seems to work nice, I rearranged the Pb blocks in my shield, got the rate back to 4 - 5 cps.
then added the 12 mm of Sn, and made an extra inner plug from radpads, with a Sn disk.
Now t's 3 to 3.2 cps and decided to accept it.
the photo's are in the PDF.


It seems the tin does it's work, so lets do some gamma spectra's
Regards, Boris.
Attachments
block castle.pdf
(3.52 MiB) Downloaded 187 times

Martin4s
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Re: New Shield

Post by Martin4s » 11 Apr 2017, 17:39

Still Studying. Found this video to be great if you want more sample mass around the Scintillator. Goto 25:16 to see his Pb Castles. https://www.youtube.com/watch?v=_vSaAeB8850

Boris
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Re: New Shield

Post by Boris » 12 Apr 2017, 07:30

Hey Martin,

If I would build a new castle I would use leaf lead or roof lead, but i guess that its not so available in your part of the globe.
Its easy to make a big roll, some aluminium tube in the middle and alu sheet on the outside, use giant air duct hose screw clamps.
From a health and safety perspective I'm against casting lead, from a practical side cast rings that you can stack...

The best construction is to put the probe in from the top side, and have a little door on the horizontal bottom side...
If you make a roll you only need a small plug in the center.

Do not use plaster or plaster of paris to cast lead, this will end in a lead coated garden and serious burns, the steam will cause a big blow-out because the plaster attracts moister from the air.

I'm considering to use a gas tank, and weld a door on the bottom side about 10 cm above the floor, if i can find some spare time...
as a safety measure I always fill a empty gas tank with water, en leave it overnight before it meets the plasma cutter...

work safe, and many happy scrapyard trips! Boris.

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sgt_bear
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Re: New Shield

Post by sgt_bear » 23 Apr 2017, 05:15

Is it possible to reverse copper and tin?

I want to build a round shield, using a steel pipe with a copper pipe inside (centered) and then fill the gap between the steel and copper with lead (about 30mm of lead). Sadly, tin has a lower melting point than lead.

Does it matter what material comes first? Or could i line the copper pipe with tin inside?
- Jonathan from Switzerland

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MartinM
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Re: New Shield

Post by MartinM » 23 Apr 2017, 18:46

Yes, the order is important as it gradually reduces the XRF energy.
Pb: ~ 85 keV
Sn: ~ 25-28 keV
Cu: ~ 8 keV
Al (usual detector case material): ~ 1.5 keV
Martin Malik, http://www.hwinfo.com

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