Bicron NaI ?

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tolson1118
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Bicron NaI ?

Post by tolson1118 » Sat Jul 01, 2006 11:38 pm

I recently aquired a Bicron NaI detector without any base or documentation. It has 14 pins but they are smaller and dont seem to be in the standard position(There is a gap between the 1st and 14th pin).
Would the anode and cathode on this be the two pins next to the gap?(1,14)
Also how would i find the correct value of R for the dynode resistors.

The model# is 1.125MW2.125/1.125
the 1.125x2.125 crystal seems to be a strange size
The S/N is JL-172, also the housing is at cathode potential.

I was just wondering if you guys have any tips on getting this hooked up and running.
thanks,

Thiago Olson
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tolson1118
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Re: Bicron NaI ?

Post by tolson1118 » Sun Jul 02, 2006 1:48 am

What resistance for the dynode string would be used for the preamp/MCA route?

it would require a base with two bnc connectors correct?
one for hv, and the other for the signal.

Thanks,

Thiago Olson

Jon Rosenstiel
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Re: Bicron NaI ?

Post by Jon Rosenstiel » Sun Jul 02, 2006 2:55 am

I've got two Bicron P-14 bases that I connect through a preamp (Ortec 113) and then to my mca. Total dynode chain resistance measures about 6.8 Meg.
Follow this link to a Bicron pdf that Carl posted last year.

viewtopic.php?f=13&t=5615#p37633

I think you've got a pmt without a glue-on base, the pins appear to be coming directly out of the pmt's glass envelope.

Jon Rosenstiel

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Carl Willis
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Re: Bicron NaI ?

Post by Carl Willis » Sun Jul 02, 2006 3:53 pm

Hi Thiago,

You've got the base of the PMT itself as Jon said, if I see the photo correctly. The regular socket assemblies for the P12 / P14 bases will be too large for it. Without calling Bicron or finding out what PMT they used, the pinout may be somewhat ambiguous. The dynode chain needed to give you a linear signal, however, will be the same as that in either a P12 or P14 socket. Resistors in the vicinity of 500 kOHM, capacitors in the 0.01 - 0.02 uF range should work fine.

Another point to make is that this is what is called an "end well" crystal. They are not so great for spectroscopy because of the large surface area to volume ratio. 12% resolution on Cs-137 (662 keV) would be considered decent for such a detector.

Hope this helps,
Carl
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Richard Hull
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Re: Bicron NaI ?

Post by Richard Hull » Wed Jul 05, 2006 3:59 pm

I have several of these tubes. They do use a wierd socket. The pin size is the same as the common old 7 and 9 pin radio tubes. I will try and post some images of the base and dynode sockets.

This is a 1" well detector for liquid scintillation work.

Richard Hull
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Tman
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Re: Bicron NaI ?

Post by Tman » Wed Jul 05, 2006 9:34 pm

Thanks Richard,
It will be nice to find out what pin goes with what.
right now im clueless. (didnt call Bicron)
I'll try to make a socket to convert this over to the standard 14 pin Bicron base for a preamp socket.
Or I might just try to hook It up in the 2 cable fashion to use with a homemade preamp.

-Thiago Olson

Alex Aitken
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Re: Bicron NaI ?

Post by Alex Aitken » Thu Jul 06, 2006 12:16 pm

To the best of my ability, this is the existing chain.

Pin 13 to pin 14 with a 10M.
to pin 12 with an 8.2M
to pin 2 with an 8.2M
to point 'A' with an 8.2M
to pin 3 with an 8.2M
to pin 10 with an 8.2M
to pin 4 with an 8.2M
to pin 9 with an 8.2M
to pin 5 with an 8.2M
to pin 8 with a 15M
to pin 6 with a 15M
to pin 7 with a 15M

Pin 10 is connected to point 'A' with a variable resistor, the center tap is connected to pin 11.

Pin 1 apears unconnected.

Numbering is as usual clockwise from the gap looking from underneith.

At the moment I don't know which is the photocathode, my meter is mislaid. Whichever end has the lowest resistance to the case should be the photocathode end. There is a wire to pin 7 and a wire to pin 13. No evidence of a third wire, we should be able to guess.

For linear pulses you will need to alter the resistance values, and add some capacitors to the anode end.

I also have one of these with base and plan to use it as a semi serious test of an MCA before taking the plunge with rather more expensive crystals. I think Carls resolution estimate might be a bit overoptimisitic. I may have seen one of these rated 27% or so. I think these things get used for tritium counting normally, very weak beta, which should give an idea how little crystal is actually needed.

I played with this tube a few years ago with an oscilloscope, only aquired an MCA recently.

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Richard Hull
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Re: Bicron NaI ?

Post by Richard Hull » Fri Jul 07, 2006 4:35 am

As promised I attach two images. One a photo of the proper Bicron socket and matching inline preamp. The other a crude hand drawing of the socket looking at it from the bottom.

All resistors are 1 megohm unless marked otherwise. The three black circles are disk caps and are all .01ufd @ 200V.

Richard Hull
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MVC-002F.JPG
MVC-002F.JPG (125.87 KiB) Viewed 2477 times
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Starfire
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Re: Bicron NaI ?

Post by Starfire » Fri Jul 07, 2006 6:35 pm

Some previous ;-

viewtopic.php?f=13&t=5615#p37633

For pre-amp info, check out Carls product reveiw ;-

viewtopic.php?f=13&t=5616#p34060

.

Alex Aitken
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Re: Bicron NaI ?

Post by Alex Aitken » Fri Jul 07, 2006 6:54 pm

Worth underlining that the schematics are fine in the pdf in the first link but the pin out is wrong for this tube.

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