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

[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.

Richard Hull

[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.

[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.

Richard Hull

[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?

[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.

[richnormand]

@ 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.

[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.

[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:

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.

PMT

Scintillation crystal LiI(Eu)

plastic spacer ring

The crystal and light pipe can be removed by careful filing through the aluminum can. The entire assembly has a potting compound around it.

LiI crystal and lightpipe removed, the crystal is extremely hygroscopic and clouds instantly

LiI crystal and lightpipe removed, the crystal is extremely hygroscopic and clouds instantly

Crystal dissolved off in water

The remaining lightpipe appears to be made of acrylic

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

[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

[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.