Russian corona counters get new life

This area is for discussions involving any fusion related radiation metrology issues. Neutrons are the key signature of fusion, but other radiations are of interest to the amateur fusioneer as well.
Post Reply
User avatar
Steven Sesselmann
Posts: 2096
Joined: Thu Aug 11, 2005 1:50 am
Real name: Steven Sesselmann
Location: Sydney - Australia
Contact:

Russian corona counters get new life

Post by Steven Sesselmann » Tue Nov 24, 2015 12:19 pm

Like many of you here on the forum I invested in some Russian neutron detectors, but like most of you I also found out that they were pretty hopeless, they had a noisy signal and a poor pulse which hardly made it above the nose. To be honest i gave up on the project several times, but every now and then when I had some time to spare I gave it another go. Eventually, thanks do David Housley for suggesting a Schmidt trigger it all came together.
chm-12.JPG
SNM-12
This is just one of many different kinds for sale on eBay and from Sovtubes.com
raw pulse.JPG
Raw pulse
The raw signal from the detector is hopelessly noisy, it's all over the place and you have to wait forever to catch a pulse, sometimes 10 minutes between pulses when you don't have a source.

I designed a simple preamplifier (with some help from David Housley...thanks) it has an adjustable LLD and hysteresis, so it can be used on different tube types. The detector is completely blind to gamma and not sensitive to EMF, I usually test for EMF by turning the fluorescent lamps in my workroom on and off.
The circuit board has 25 turn Bourns trimmer potentiometers for the threshold and the hysteresis adjustments.
gs-neutron-pcb.jpg
Circuit board
The input power for the SNM-12 detector (500V) can be provided by one of my GS-1100A or GS-1100-PRO but can also be provided by any NIM power supply. The output signal is at line level and can be plugged straight into a PC Line In and be analysed by PRA or any of the other open source programs.
clean-pulse.png
Output pulse
I took the detector in to Marek at the University of Sydney, where they have a 2.2 x 10^6 AmBe neutron source, and we were getting 50 cps at 23 cm distance from the source, which after allowing for some paraffin blocks and lead worked out to a detector efficiency of 15% (nvth).

These Russian tubes are quite old and I imagine their efficiency not may be quite what they were 30 years ago, but they would certainly be useful in a fusor lab.

I have a stack of these tubes so if anyone is interested please PM me, or post a reply. For those of you who own Russian corona tubes I am happy to sell the boards only.

Steven


gs-neutron-150-a.jpg
GS-Neutron
The moderator is manufactured from black HDPE and measures 90 mm Ø, and the whole detector stands about 340 mm tall.
gs-neutron-150-b.jpg
Close up
A green LED indicates that the power to the preamp is switched on. The HV connector is an SHV and the signal connector is a standard BNC connector, best to have two different kinds of connectors, as connecting the HV to the signal would certainly kill the detector.
battery.png
Battery holder
The battery is held neatly in the base of the detector, in the tests I have done so far, the battery life is around 50 hours (2-3 days).
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG

User avatar
Richard Hull
Site Admin
Posts: 10936
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Russian corona counters get new life

Post by Richard Hull » Wed Nov 25, 2015 2:28 am

Looks interesting, indeed. Some young fusion aspirant might try one of these and give us a report. Some sort of calibration might be needed for fusor use relating the count rate to isotropic emission.

Richard Hull
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.

johndmcmaster
Posts: 11
Joined: Fri Mar 13, 2015 6:36 am
Real name: John McMaster
Location: Mountain View, CA
Contact:

Re: Russian corona counters get new life

Post by johndmcmaster » Thu Nov 26, 2015 12:44 am

I've tried several times to get my SNM-11 and SNM-32 to work without success. Thanks for the post...will see if I can have any success following your reccomendations. But it sounds like one takeaway is that if you are looking for a serious, high quality sensor...they aren't it.

User avatar
Steven Sesselmann
Posts: 2096
Joined: Thu Aug 11, 2005 1:50 am
Real name: Steven Sesselmann
Location: Sydney - Australia
Contact:

Re: Russian corona counters get new life

Post by Steven Sesselmann » Thu Nov 26, 2015 1:13 am

johndmcmaster wrote:I've tried several times to get my SNM-11 and SNM-32 to work without success. Thanks for the post...will see if I can have any success following your reccomendations. But it sounds like one takeaway is that if you are looking for a serious, high quality sensor...they aren't it.
John,

I absolutely know how frustraling these tubes can be, have grey hair to prove it.

Not sure what you mean by "serious high quality sensor", in my mind a 30 year old tube is "pre-disastered" (Robin Williams expression*) anything that could have gone wrong would have gone wrong, so if it still works its a good one. The only thing you would need to do is put it up against a calibrated neutron counter and get an accurate number for the efficiency.

I could send each one to ANSTO here in Sydney for calibration, but it would add $450 to the price.

http://www.ansto.gov.au/BusinessService ... libration/

Steven

*Can't recall which movie it was, an estate agent is showing him a house and while they are watching a small plane crashes into the house, he says I'll take it, it's pre-disastered...
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG

johndmcmaster
Posts: 11
Joined: Fri Mar 13, 2015 6:36 am
Real name: John McMaster
Location: Mountain View, CA
Contact:

Re: Russian corona counters get new life

Post by johndmcmaster » Sat Dec 12, 2015 7:19 pm

Received board, will hopefully play with it soon

johndmcmaster
Posts: 11
Joined: Fri Mar 13, 2015 6:36 am
Real name: John McMaster
Location: Mountain View, CA
Contact:

Re: Russian corona counters get new life

Post by johndmcmaster » Sun Dec 13, 2015 5:32 pm

One of the problems I was having before was manually finding a pulse on the scope let alone automatically. As this board still requires some tweaking, lets confirm I have a good starting point before I mess with it.

I started off using a bare (ie no metal case shielding) SNM-11 tube. The noise was so high that I couldn't really pick out anything I thought were neutron pulses. It had long leads from alligator clips etc.

Someone loaned me an encased SNM-17 that I believe is from eBay seller cgroat3573. Although I don't have measurements handy from previous setup (not to mention its not the same tube type let alone the tube itself) I believe ambient noise went down considerably. Most everything is shielded now save a few resistors clipped to binding posts (see attached).

Test setup:
-Tube: SNM-17 (max voltage 2800 V)
-Power supply: Ortec 456 @ 2500 V
-Current limiting resistor: 100 M
-Shunt: 100 k resistor to ground in parallel to scope (1 M)
-Source: Am-Be, Am-Th (on loan from friend that said he used them before)
-Moderator: plastic sheets, mineral oil randomly thrown about
-Scope: Agilent 54622D

I catch a pulse like shown every few seconds. Does attached look about like expected raw signal on a scope? One thing I noticed is that your pulse has opposite polarity. If not can start a separate thread to diagnose that first before trying out your board.

Other: I started collecting info on Russian tubes here: https://siliconpr0n.org/nuc/doku.php?id=russia:start
20151213_010252.jpg
20151213_010326.jpg
20151213_010340.jpg

User avatar
Steven Sesselmann
Posts: 2096
Joined: Thu Aug 11, 2005 1:50 am
Real name: Steven Sesselmann
Location: Sydney - Australia
Contact:

Re: Russian corona counters get new life

Post by Steven Sesselmann » Sun Dec 13, 2015 8:45 pm

John,

The raw trace from the detector coupling of a corona counter should give you a randomly disorganised baseline with an occasional negative pulse. What I see on your scope is a regular zig zag trace and a positive pulse, indicating it may be electronic noise from your PSU. To see the pulse you need to set the scope to 10 mV steps and the time scale to around 10 µs. Forget about catching it manually, you need to to set a trigger as it could take several minutes and you might just happen to blink your eyes.

It's very important not to turn the voltage up too high because these corona tubes become geiger counters once you exceed a given threshold, so if you suddenly start seeing beautiful big pulses every couple of seconds on your scope, you probably went to far.

The GS pre-amp will invert the pulse and produce an easy to detect positive pulse.
gs-neutron-tuning.jpg
Tuning Instruction
gs-neutron-tuning.jpg (48.66 KiB) Viewed 3517 times
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG

Post Reply