Looking for a 3" NaI(Tl) Crystal

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Brian McDermott
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Looking for a 3" NaI(Tl) Crystal

Post by Brian McDermott » Thu Dec 01, 2005 11:25 am

After finding a 3" PMT for 20 bucks, I need to get a crystal to go with it. I'm mainly interested in Gamma ray detection, so I'm looking for an NaI(Tl) crystal to go with this PMT.

The diameter is essentially locked in at 3" but are there any recommendations as to the thickness? How much would a 3x1, 3x2, or 3x3 crystal cost if purchased new? Don Orie dosen't seem to have any at the moment, so (apart from eBay) are there other sources for these things?

Alex Aitken
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Re: Looking for a 3" NaI(Tl) Crystal

Post by Alex Aitken » Thu Dec 01, 2005 11:04 pm

For gamma spec a 2x2 inch crystal will normally get you better resolution than a 3x3 and much better than a 1x1. You'd go with larger crystals for sensitivity only and its probably worth going the BGO route for that sort of thing.

A 2x2 crystal in sealed assembly from bicrondirect is currently 280 USD.. A 3x3 crystal is currently about 780 USD. They used to sell PMTs and the numbers were about 300 for a 2 inch PMT, 300 for the crystal or 600 to 700 for a sealed unit.

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Brian McDermott
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Re: Looking for a 3" NaI(Tl) Crystal

Post by Brian McDermott » Thu Dec 01, 2005 11:28 pm

The goal here is high-sensitivity general survey, not spectroscopy. A BGO would certainly be nice, but I could buy a car for the price of a suitably sized BGO crystal for this PMT.

Q
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Re: Looking for a 3" NaI(Tl) Crystal

Post by Q » Fri Dec 02, 2005 12:15 am

heh, very true!
have you considered scintillation plastics? i know they aren't terribly sensative to gammas, but might be a more affordable option. not sure, but there might be a specific plastic for gamma detection.... well after a brief check of the bicron site, the general purpose bc-412 is listed for gamma detection. i'm currently finishing up a pmt unit using a large 3x3x2 block of bc-400 plastic. we'll see how sensative it is to gammas when finished.

Q

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Brian McDermott
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Re: Looking for a 3" NaI(Tl) Crystal

Post by Brian McDermott » Fri Dec 02, 2005 1:00 am

I've considered the plastics and I actually have a smaller 1.5" BC-400 scintillator that is about 15 times as sensitive as my pancake probe. But like you said, it isn't as sensitive to gammas, and that is what I'm interested in detecting. I'll check out the 412 and see how it compares to NaI(Tl). Given what little experience with scintillators I have, perhaps Carl or Richard could comment.

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Re: Looking for a 3" NaI(Tl) Crystal

Post by Alex Aitken » Fri Dec 02, 2005 10:18 am

If all you want to do is count pulses, and more is better, then I'd question if you want a crystal scintillator at all. Some of the most cost effective detectors you can build are just small tanks of scintillating solution, eg POPOP in toluene, or anthracene mixtures. Ultimatly the detection efficiancy is going to be limited most by weight, dense crystals just get you a physically small size. I'm not convinced the 3inch size of your PMT makes any real difference. A smaller one would give you less noise and not make a lot of difference to collected pulses.

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Brian McDermott
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Re: Looking for a 3" NaI(Tl) Crystal

Post by Brian McDermott » Fri Dec 02, 2005 10:47 am

I considered liquid scintillation, but how portable is such a setup? If this is a viable route, how pure does the toluene need to be? Hardware store? Technical Grade? ACS Grade?

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Richard Hull
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Re: Looking for a 3" NaI(Tl) Crystal

Post by Richard Hull » Fri Dec 02, 2005 3:45 pm

If you are using this for just sensitive gamma detection then PLASTIC is #1 within any budget vs sensitivity argument.

OE technology is the #! source for plastic! Don is sitting on a mountain of the stuff!

I have long had in my possession a 6"X6"X4" block of B400 material and have a brand new Hitachi 5" pmt with Socket and mounted Preamp.

I have always planned to link the two for a super snooper for prospecting and the ultimate gamma device, but sheer indolence coupled with a thousand other projects milling about me have kept the two items apart for so long. I dare not think what such a volume of detection would produce.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Re: Looking for a 3" NaI(Tl) Crystal

Post by Q » Fri Dec 02, 2005 8:31 pm

i'll second richard's suggestion for a source of scintillation plastic. OE tech has a lot of it and for cheap! plus, don is really great to deal with.

Q

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