Board Mounted LiI(Eu) scintillators - repost in neutron detection

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Jim Kovalchick
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Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by Jim Kovalchick » Fri Feb 01, 2013 5:34 pm

Transfered from a trading post item:

Some ebay miniature scintillators became available and some folks were taking a look at trying them. They were Scionex scintillators mounted on miniature R 7400 Hamamatsu PMT's.

some links for those who were interested:

The original Ebay link was http://www.ebay.com/itm/251221362787

http://sales.hamamatsu.com/assets/appli ... 003E01.pdf

http://xa.yimg.com/kq/groups/16117819/3 ... ector1.pdf

Thanks to Chris Bradley for cluing the rest of us in to these interesting little devices. If anyone manages to get any of these and trains them to do neat tricks, this would be a good place to post it.

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Rich Feldman
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by Rich Feldman » Fri Feb 01, 2013 8:56 pm

Thanks for taking this to the detection forum, Jim.
Note that Trading Post -was- the right place to originally bring up an ephemeral sale on ebay.
Thanks to Chris for spotting and reporting it, even with the typo (LiL indeed! LOL).

The writer of the .pdf in yimg link apparently obtained 8, of which 4 were no good. We don't know if they came from this week's ebay seller, who gets more from time to time & and sells 'em off. He/she got a flurry of feedbacks about them last summer. About five were thumbs-up, and one was neutral, saying "all of them are bad".

My offer for three specimens, in hope of getting at least one good one, has been accepted.
Naturally I'll be inspired to test them ASAP, and hope a smoke detector or x-ray source will give some action if the PMT's are OK. Then would have to explore pulse-sorting land, with plenty of tourist info on this forum.

Over the years I've scrounged a small armload of bare PMT's, including three from Kazakhstan during last summer's adventure with Carl W. et al. But have yet to electrically bias one.

Rich
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Chris Bradley
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by Chris Bradley » Fri Feb 01, 2013 9:36 pm

Rich Feldman wrote:
> Thanks to Chris for spotting and reporting them, even with the typo (LiL indeed! LOL).
No worries - I corrected my post title ... after I saw you repeat it in your reply!

Good luck with your samples.

PS - If these are from the 'polimaster' type pager dosimeters, then it may be worth noting the rated sensitivity of those is 1.3 counts cm^2/thermal neutron, and 0.05 to a Pu[alpha]-Be spectrum neutron.

see ...

viewtopic.php?f=13&t=6286#p41707

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Rich Feldman
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by Rich Feldman » Fri Feb 01, 2013 10:10 pm

Please excuse a short and humorous (?) sightseeing detour from the fusor highway.
That LiI/LiL mixup reminds me of a double error I spotted a few years ago, which has permeated an Internet niche like mutated DNA.

Cream of tartar (potassium hydrogen tartrate) is a chemical used in foodstuffs, produced as a byproduct of the wine industry. It also is popular for crystal-growing, often after conversion to Rochelle salt.

Cream of tartar is sold next to herbs and spices in grocery stores and online stores.
Practically all of the latter say, in the botanical name field, Adosonia gregoril.
e.g. http://desertbotanicals.com/store/produ ... cts_id=395

The "correct" botanical name, if any, would be Adansonia gregorii -- the cream of tartar tree. It's an Australian relative of the baobab trees of Africa and Madagascar.

The genus name is probably wrong because of a phonetic transcription error.

The species name (gregoril with an L at the end) must be wrong because of a typographical transcription error, and/or someone in the supplements business who was unfamiliar with the double-eye ending in taxonomy. Or, God forbid, dumbed it down on purpose.
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Rich Feldman
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by Rich Feldman » Thu Feb 14, 2013 8:11 pm

My Scionix detectors arrived promptly (more than a week ago), carefully packed to avoid any damage in shipping. Picture 1 shows how eensy weensy they are. Seller included hard copies of the yimg posting and hamamatsu datasheet that Jim pointed out.

As you can see, I had opted for the "bent or broken pins" grade. It appears that many of the straight pins had once been bent flat. After straightening, before they reached my hands, some were barely hanging on. A harsh look could make them fall off (Picture 2). Bent flat would be more easily usable.
Can anyone tell us if the "all pins intact" grade devices are in condition to plug into a socket, or to solder onto a board?

Here is my plan A for restoring the connections, subject to change if a better idea appears. Too bad I don't have an apprentice to perform the rework. The weak-pinned device is rigidly attached to something with a standard 10-pin connector, and 10 short jumper wires are soldered point-to-point. Photo 3 shows a test connection between a 30 AWG wire and a broken-off pin. The black rubbery potting compound is hard to dig out with an X-acto knife, but easy to remove with a sharp, hot soldering iron tip. Will need to think about whether surface leakage currents are an important consideration.

For specimens with most pins intact, Plan B might be easier. The broken pins are extended with short, parallel wires. Then all 10 pins are soldered to a piece of breadboard material with plated-through holes on grid, which can serve as the tube holder.
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by richnormand » Thu Feb 14, 2013 9:04 pm

""""Can anyone tell us if the "all pins intact" grade devices are in condition to plug into a socket, or to solder onto a board""""


Got one of those "all pins intact" on the way. Will let you know once it shows up and see if the extra $$s were worth the trouble. By now it looks like he ran out of the "all pins intact" units.

With the idea of soldering a small extension are you running in potential issues with the heat cracking the glass (if it is glass) or solder not thinning the pin without lots of heat?


Have fun!

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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by Chris Bradley » Thu Feb 14, 2013 10:22 pm

Rich Feldman wrote:
> Bent flat would be more easily usable.

That's the impression I got. For hobbyist purposes where we're likely not to solder to a board anyway, this looks 'obviously' (!?) like a case where you would want to simply solder wire ends straight to the bent-flat leads, and leave them bent. The end could then be potted over, if you wanted to do that, to give mechanical robustness to what would then be a set of flying leads soldered onto those legs.

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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by richnormand » Thu Feb 21, 2013 7:25 pm

<<Can anyone tell us if the "all pins intact" grade devices are in condition to plug into a socket, or to solder onto a board? >>

As promised here is a photo of my unit. All pins accounted for, as you can see. Looks in good shape.
Well packed and fast shipping.

One caveat however: one of the pins is not as rigid as the other ones. From the deflection angle under the microscope it looks like it might be broken at the PM base, a few mm under the potting compound. Most likely being held in place by it. I'll have to power it up to find out......
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by Rich Feldman » Thu Feb 21, 2013 10:43 pm

Hi Rich. So far, it looks like your extra money for complete pinnage was well spent.

Meanwhile, I am eager to get at least one of my detectors wired up. Have been thinking of using some sort of electrically conductive resin instead of solder, for connections to pin stumps below the black level. Low resistivity is not a critical requirement here!

Which product to get? What are their shelf lives?

Dennis Brown has spoken well of two-part "Silver Conductive Epoxy" from MG Chemicals: viewtopic.php?f=2&t=1048#p7775
A competing industrial product is from Chemtronics: http://www.chemtronics.com/products/ame ... CW2460.pdf

MG also makes a lacquer called Silver Print, 842-20g, or in pen form as 8420-P. http://www.mgchemicals.com/downloads/pd ... ts/842.pdf I bet it's similar to stuff sold at auto parts stores, for repairing window defogger grids. [edit] Permatex 15067, which served me well for the labeled purpose. Years later, reconstituted some that had dried up in the bottle, and repaired a damaged variable resistor.

At the low-cost end, there seems to be a new carbon-based product called 'wire glue". http://www.amazon.com/gp/product/B000Z9H7ZW Perhaps similar to Aquadag, but thicker?

Any first-hand reports would be welcome. Thanks!
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by richnormand » Thu Feb 21, 2013 11:56 pm

I have used these two products (or similar formulations) over the years.

The silver epoxy was used in building diode and RF sputter targets. It works well, can withstand some temperature, has decent thermal conductivity, but you need a rough and very very very clean surface to get good adhesion. Some need curing, you do not want to damage the scintillator.

The silver print is a paint (can be diluted in acetone) that has little mechanical strength and cannot really carry much current. Easy to remove. Conductivity gets better as it dries until (or if) it flakes off. May be OK for your application but use very fine wires as a loop, just like the solder.

As far as shelf life I had to keep the epoxy in the fridge and use it before a year or so despite the manufacturers claim for a longer "best before date".

The silver print will tend to get sticky but you can add solvents and it will last a long time. Getting the bottle opened is my biggest issue as the cap sticks well....

Also silver print is easy to get in small quantities. If I remember the silver epoxy had to be purchased in larger amount.

One final comment, due to its viscosity and small size of the contact the epoxy might be difficult to work with on the pin stub at the PM glass transition. But if it sticks OK it will be more rugged than the silver print but difficult to remove once cured. OTOH if you try the silver print, it is easy to remove if it does not work well and the small bottle will surely be of use in many more applications (like making good contacts to the battery in my car remote FOB)... and such.

I would stay away from the carbon "wire-glue". Used two different products with ho-hum results. Your mileage may vary but I dumped them. Perhaps others here had better results with different brands?

Hope that helps. Keep in mind this statistical survey has only one data point (me) however. So I would be interested of hearing from other people!!!

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