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

Posted: Thu Feb 07, 2019 12:35 pm
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..

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

Posted: Sun Apr 21, 2019 11:56 pm
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.

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

Posted: Mon Apr 22, 2019 4:09 am
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

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

Posted: Tue Apr 23, 2019 1:22 am
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.

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

Posted: Tue Apr 23, 2019 4:08 pm
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.

Richard Hull

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

Posted: Tue Apr 23, 2019 10:50 pm
by Jim Kovalchick
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.

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

Posted: Wed Apr 24, 2019 6:13 am
by Richard Hull
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