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 »

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

Post by Rich Feldman »

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 »

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

Post by Rich Feldman »

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 »

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 »

""""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 »

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 »

<<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 »

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 »

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

Post by Richard Hull »

Most pins are SS. If it were my setup, I would use 50:50 tin indium melts at a low temp ~300F and wets glass, porcelin, SS, etc. You might try woods metal melts 146 deg F and put into the area a pretinned CU wire to attach electrically.

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

Post by richnormand »

Thanks for the input Richard.

Just ordered a small spool of tin indium solder from flea-bay.
Does it need something special for flux?

I'll post the result on my second (several pin missing altogether) unit when I try it.
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by Richard Hull »

Cleaniness is a must. Usually a mild alkaline solution of NaOH followed by a distilled water wash off is enough to prep the item to receive the solder. There is no fluxing necessary.

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

Post by Rich Feldman »

They're back!
LiI(Eu) scintillators / PMT's in cans with bent and broken pins.
But now the ebay seller is "rockcodfred"; last couple times it was "kephis", IIRC.
http://www.ebay.com/itm/Scionix-Holland ... 1861232106
Their detector crystals are 60% as large as the ones in NeutronRAE ii.
This might inspire me to try biasing the one I wired up a couple years ago.
How far did you get with yours, Rich Normand?
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron

Post by Rex Allers »

It doesn't change anything in the discussion, but I'm pretty sure ebay seller(s) "rockcodfred" and "kephis" is the same person. Not sure why the newer identity.
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron

Post by richnormand »

P2245090 (Medium) (Small).JPG



@ rich
"How far did you get with yours, Rich Normand?"

I got two units a while back . One with all pins, one with damaged pins. Same result with both.

I used a 50/50 tin indium solder to keep temps low as initially suggested by Richard. It worked very well but contacting the pins was not the issue.
The "all pins intact" unit did have a pin loose, being held by the potting compound. On clearing the stuff it was obvious the the pmt glass was indeed broken/cracked as viewed on the microscope.
Same with the other one.


All I got was noise and bursts from the pmt as I raised the voltage as both were gassy. So i decided on another route.

I took an x-ray of the assembly and got a Buehler low speed diamond saw from fleabay and decided to cut the pmt out.
Did not have time yet to polish the detector/light conduit to test it with another pmt yet but it look like I did not damaged anything.
I did the cut just before the pmt front plate to try to keep the whole thing air tight.

The project has fallen a bit off the priority list due to lots of more urgent things to do... but is not dead yet.

For those interested I found several papers, company specs and other info on these. I could post these if you want.
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron

Post by Rich Feldman »

Nice work Rich.
I like how the iodine stands out in the radiograph. https://en.wikipedia.org/wiki/Mass_atte ... cients.png

My record of finishing projects is inferior to yours. Here is how far my best specimen got in March, 2013. A worse one is shown after gentle clamping in a standard EMT compression fitting. Here they are perched on a block of zirconium, but that's a different story. The detectors are still in a box with that indium solder you sent me.
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by Andrew Seltzman »

De potting of the scintillation assembly:
I got a few of these detectors as freebees and decide to de-pot one:

Tube assembly with back potting compound removed, fairly easy with a heat gun:
IMG_20181209_183736124.jpg
PMT de-potted, takes a little more effort, but still possible with a heatgun and fine screwdriver, the PMT is glued to the lightpipe with an optical compoint, but comes off if wiggled. You need to clear the glue off from around the sides of the lip first.
IMG_20181209_204946022.jpg
PMT
IMG_20181209_205131101.jpg
Scintillation crystal LiI(Eu)
IMG_20181209_205144228.jpg
plastic spacer ring
IMG_20181209_205259465.jpg
The crystal and light pipe can be removed by careful filing through the aluminum can. The entire assembly has a potting compound around it.
IMG_20181209_212725459.jpg
LiI crystal and lightpipe removed, the crystal is extremely hygroscopic and clouds instantly
IMG_20181209_212836572.jpg
LiI crystal and lightpipe removed, the crystal is extremely hygroscopic and clouds instantly
IMG_20181209_213153650.jpg
Crystal dissolved off in water
IMG_20181209_214132296.jpg
The remaining lightpipe appears to be made of acrylic
IMG_20181209_214850401.jpg
End notes: It's impossible to remove the crystal without destroying it, the PMT cam be removed easily. The crystals are well potted and will likely be good even if the PMT is dead. It's likely possible to use a glass or plastic lightpipe spacer to couple the crystal to another PMT. A Hamamatsu H7828 Photomultiplier Module might work:
https://www.ebay.com/itm/233022956291
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by vince_Darmancier »

I have just gotten 3 of these Scionix with all pins intact. looks like he has 5 left..

https://www.ebay.com/itm/Scionix-Hollan ... :rk:1:pf:0

i also found this one..
https://www.ebay.com/itm/5-Scionix-Holl ... :rk:2:pf:0

But i was wondering if the pins connect to a resistor chain like normal PMT and run on high voltage?
Or does it has a different wiring set up?
any available diagram?
Much oblige
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by Rich Feldman »

Yes, you need to provide the HV and resistor string.
Pinout is given in Hamamatsu PMT datasheet, or you can trace pictures from earlier in this thread.

Please let us know, yes or no, if you get a normal PMT signal from any of those units. With or without neutrons. I promise to complete that exercise for the unit in my 2013 picture, but not before testing my BF3 tube. (Needs a bias supply that goes much higher than the 0-1000 V unit on hand.)

[edit] Andrew included a picture of LiI crystal being dissolved in water.
Now Li+ and I- both have well established uses in health care.
So the combined solution might be good medicine, for individuals in one section of a Venn diagram. Unless a trace of europium is bad for all. :-)
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by vince_Darmancier »

I followed the exact instructions and used the recommended value for the resistors and capacitors . i then slowly increase the voltage untill the magic blue smoke was released...
FAIL
no signal ,

but i found a He3 tube fr $95 on ebay that seem to work perfectly with my eberline counter.
It reads between 4 and 11 count of background every 15 minutes or so.

The LiI detectors/PMT are really tiny and difficult to work with , i have 2 more left and plenty of resistors and capacitors so i might try again in the future..
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by Rich Feldman »

Following one of those old ebay links, we find "kephis" and the familiar detectors there today.

Now he/she is offering some on their application circuit boards, from SAIC model GR135, for about the same money. I bet that means no broken-pin issues, and ancillary stuff like PMT voltage divider chain will be already wired up. Seems like a project Joe Gayo would enjoy. Anybody familar with the SAIC product and its specs?

Ebay picture shows a neutron moderator part made to fit around the scintillator assembly.
saic.JPG

Now I wonder if the NeutronRAE or Polimaster personal dosimeters are big enough to come with effective, purpose-built moderators inside. We know they use the same scintillator material, in somewhat larger pieces. Bern Bareis, if you read this and still have your NeutronRAE, would you mind taking a look inside it?

IIRC, Polimaster datasheet has separate sensitivity numbers (counts per neutron) for "thermal" and "Pu-Be spectrum" neutrons, with a 10:1 or 20:1 ratio.
NeutronRAE datasheet in 2015 gave a 2:1 sensitivity range without specifying the energy. Same datasheet said the detectable neutron energy range is thermal to 14 MeV. One user thought the sensitivity numbers implicitly applied to any detectable energy distribution. I was among those who did not read it that way.
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by Andrew Seltzman »

Here are some x-rays of the board with the LiI(Eu) unit removed
gr135pmt3b.jpg
gr135pmt3.jpg
gr135pmt2.jpg
gr135pmt1.jpg
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by Jim Kovalchick »

To answer the question about the neutronrae, it has no moderator in it.

.

When using the neutronrae as a dosimeter as it was intended, remember that it sits against a human body which tends to moderate nicely.
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Re: Board Mounted LiI(Eu) scintillators - repost in neutron detection

Post by Richard Hull »

Yes my neutron detector (3He) is moderated by water. The human body is nothing but a big bag of water.
I have a lot of wood around the neutron detector which moderates as well, but has a minuscule effect due to the low output of the fusor and the separation from the device and detector.

Some here tend to forget that neutrons scatter and slow down in a lot of stuff.

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