My lead house for spectrometer

[lehoslav]

Hi guys!
I would like to show you a lead shielding I made for my spectrometer.
Its core is made of lead sheet (2,5 mm thick), rolled on a copper pipe (with 108 mm external diameter and 3 mm thick walls). There is also a lead bottom on which a copper circle is put. I also made a lead lid covered with copper sheet from all sides. The effective thicknes of the lead walls is ca. 2 cm, the bottom and lid are slightly thicker.
The core of the shielding is put into a steel bucket, covered with a steel sheet from above and sealed with silicone glue. I also made a small wooden platform with plastic wheels so that I can freely move the shielding from its place (the overal weight is over 60 kg).
The lead house is quite effective. Without it I get ca. 80 ips on my spectrometer, in the housing the readings are about 4 cps (in fact, even slightly lower), just see the photos with PDS-100G :)
The overall cost was ca. 500 USD + one long evening work in the cellary :)
I will show some interesting spectra soon!

[Geoff]

That's really nice! I like that the lead is completely enclosed.

[lehoslav]

It was actually one of my main requirements that the lead is completely enclosed. It is my living room and place of everyday work, there was just no other way from all possible point of views, beginning from the safety and ending with the aestetics.
In the attachment you can see the background measured using my spectrometer, once in the shielding and once outside at virtually the same place. 3,77 ips vs. 63,32 ips, I am really happy with the effect.

[pilgrim]

Good work lehoslav! And good result as well : my lead shield is a little less than 2 cm thick, but I only got a reduction factor of 11...

[lehoslav]

A small presentation of the shielding effectivity.
As shown before, the natural background in the shielding is about 3,7-3,8 ips.
The attached spectrum (once with the background displayed, once without) shows a measurment of a very weak sample. The exposition time was set to 18,000 seconds. The overall count rate is 4,46 ips including the backround, thus substracting the backround the count rate of the sample was only ca. 0,7 ips. However, a nice peak can be easily seen.
The peak is about 710 keV but it is probably shifted due to the unsatisfactory geometry of the measurment (unfortunately, I don't have a marinelli beaker yet; the callibration is good enough). The sample are mushrooms from a forest near to my town (western Poland), so I suppose it is just CS-137, coming from Chernobyl. Other ideas?
In any case, the shielding seems to be effective enough.

[vpozew]

Hi Lehoslav, what detector did you use to score this spectrum. Yes it is probably a small peak of CS137

[lehoslav]

NaI(Tl) 40x40 mm, the entire device is 'handmade'.

[Conor Whyte]

Very nice shield. This is in fact the same style of construction that I was proposing for my build. Lead flashing is absolutely perfect and more pure than the lead shot which is up to 10% Antimony in some cases.
Next project phase for my spectroscopy setup.

[lehoslav]

Thanks!
Before buying materials I considered using lead scrap and lead shot but then I arrived a conclusion that it is worth to pay a litte more but to be sure what the shield is really made of. The sheet I used has a certificate that it consist in 99.94% of lead.