Hello there. Sorry to bother you, but do you have any input on making a lead collimating attachment for a scintillation detector? I have several bicron nai(tl) detectors, and I’m trying to detect radioactive sources in an industrial scrap yard. But I’m getting so many different sources that it’s hard to narrow them down. I have several Ludlum meters and I am very comfortable using them… But I would like to design and make a lead collimator lens to help narrow down what part of the scrap yard the source is coming from… Then I can switch over to another meter with my pancake probe to narrow it down.
Lots of wheel weights melted and poured into a mold that the detector can fit into. At one scrap yard they got in some tungsten carbide cylinder sleeves for some sort of engine and those fit a scintillating head very nicely. You will want a pair of detectors and a meter setup so it triggers an alarm when a threashold count level is reached. I used an old analog Ludlum mode 2 that used a little proximity sensor to detect the gauge needle position. Borrowed a few nuclear sources to dial it in, one was a Cs 137 15mCi source used in a Troxler gauge and the other was a Sentinal gamma ray projector. Both items had the source exposed and put in a load of scrap steel and driven across the scale to set the low limit cutoff and dangerous level alarms. This project oriented by chance that I had a small counter that got switched on in my tool bucket and I discovered an orphan source. 😮
What is the benefit of the BGO crystal in comparison with the commonly available Scintillator materials like NaJ(Tl) or CsJ(Tl) scintillation plastics etc?
BGO is partly comprised of Bismuth. Bismuth's high atomic number (83) together with the high density of BGO (7.13 g/cm^3), results in BGO having the largest probability for photoelectric absorption out of any common scintillation material. In other words, a lot of gamma rays interact with it, compared to NaI(Tl), CsI(Tl), etc. In fact, BGO has about twice the density of NaI(Tl) (7.13 compared to 3.67 g/cm^3). Or about 7 times that of many plastics. BGO is also rugged, and does not break very easily, especially when compared to NaI(Tl). It's not hygroscopic either. But of course it has a bunch of disadvantages too, which is why it isn't that common.
I found it on eBay a couple of years ago, but sadly they seem pretty rare there. BGO has a high density, which reslusts in a sensitive detector, especially at higher energies compared to NaI(Tl) or organics. Great for uranium hunting!
any proper scintillating crystal will do, this includes and is not limited to, plastic scintillator, CsI and NaI( Tl). the coupling compound is a silicone oil that removes the air gap between crystal and PMT, this is required to reduce losses and improve effectivness.
