Fusor Forums

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

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.

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

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?

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.

@ 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.

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.

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

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

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.

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..

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.
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.

Here are some x-rays of the board with the LiI(Eu) unit removed

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.

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.

Richard Hull

Richard,
You may remember that I demonstrated the phenomenon at a previous HEAS with your fusor. I took the bare probe of my PNC-1 and used my body to thermalize the neutrons. My body liquid was darn near as good as the parafin in the detector block.

Jim, Yes, I do remember that demo and that is why my 3He tube is in a tank of water since 2002. Total absolute surrounding of pure moderator. Similar to what it would do if placed inside a suitable body cavity where the sun don't shine. Couldn't resist the illustrative humor.........

Richard Hull