Horizontal Lead shielding design for GS

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kotarak
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Joined: 07 May 2020, 05:46
Location: Brookfield, CT, USA
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Horizontal Lead shielding design for GS

Post by kotarak » 03 Jul 2021, 01:51

With my Lead shielding vertical design, I found it to be annoying to constantly remove the detector in order to access the test chamber so I decided to change the design to horizontal - this will keep the detector in place I can add/remove samples to the test chamber just by lifting a lead gate.

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I redesigned the castle so the detector is in a horizontal position and can stay in while I am only manipulating the sample and the end shielding.

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For the new design I reused the main shield sleeve from the old chamber - 6" long Schedule 40 PVC pipe with 4" diameter. There is about 0.5mm of copper foil wound directly around the pipe and a little over 1/2" of Lead sheet (1/8" thickness). The whole package is tightly wrapped with duct tape. The outer diameter is 6".
The outer shield doubles the amount of lead around the test chamber and the detector's NaI(Tl) crystal.

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For the inner shield I used 12" long section of 2" copper pipe and wound 5 turns of 1/8" thickness Lead sheet. Again, everything is tightly wrapped and covered with duct tape.

The inner shielding is twice as long as the outer sleeve (12" vs 6") and shields the length of the entire detector assembly.

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I built a special, custom wooden crate to hold the lead shielding. The base is made of 3/4" pine 6" x 16". The two sides around the large lead sleeve are glued and screwed with 2" 1/2 long decking screws to the base.
Two threaded rods, inserted in transparent vinyl tubing, together with washers and nuts re-enforce the top part, maintain the spacing of the sides while allowing the outer sleeve to be removed from the top after the inner sleeve is removed thru the front or the back. The front threaded rod (which also has a larger diameter) doubles as the front carry handle.

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The rear portion is a boxed off extension and it has 3/4 pine raiser on which the inner sleeve lays on so it aligns with the outer sleeve. A second carry handle is attached to the top of this box.
Assembly takes place in reverse order. Outer sleeve is dropped from the top into place and then the inner sleeve is inserted

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The 6" long second box section sits on top of the base and the inner sleeve rests on it. It is attached to the base from the bottom side with the same long decking screws and wood glue. A 1" "lip" is left on the back to support a lead shield cap.

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This is the end through which the GS detector is inserted and the detector position is adjusted inside the copper tube lining in order to place the front face of the crystal right against the sample.

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The front end of the chamber with the inner sleeve nested inside the outer sleeve. The white front face of the detector is visible inside the copper lining.
The bottom of both compartments is lined with 1/8" rubber lining. The threaded rod on top is a structural components as the whole crate becomes very heavy (~65 Lbs.) and it acts as a handle as well.

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After the test sample is placed in the chamber, a front shield/cap can be quickly assembled of lead bricks.
UPDATE: I built a "gate" made of 1/4" copper plate attached to 1/2" thick lead plate. The gate lifts up to uncover the test chamber. Lead bricks can still be arranged on the outside if additional shielding is needed.

ImageThe complete lead castle (v2). 4 rubber feet are installed on the bottom of the base.
While this design puts a slightly less lead (5-7mm) around the crystal than the vertical design with cast inner shielding, it is much more convenient to use and operate.
Two coats of polyurethane varnish as a finishing touch.
Andrey E. Stoev
Brookfield, Connecticut, USA

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Sesselmann
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Joined: 27 Apr 2015, 11:40
Location: Sydney
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Re: Horizontal Lead shielding design for GS

Post by Sesselmann » 03 Jul 2021, 11:27

Andrey,

Great to see the forum active again and well done on your lead shield build. Simple and effective solution.

Maybe you could spray some primer on those lead bricks and make them a bit more friendly to handle.

A sock on the detector will give it some protection against scratching..

Steven

Senketsu
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Joined: 26 Sep 2021, 21:47
Location: Poland
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Re: Horizontal Lead shielding design for GS

Post by Senketsu » 29 Sep 2021, 02:56

Great work! I also have to finally create some decent shield for a nicer gamma spectrum

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