CAMAC or scratch built detection system?

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
Maciek Szymanski
Posts: 193
Joined: Wed Nov 20, 2019 2:31 pm
Real name: Maciek Szymański
Location: Warsaw, Poland

CAMAC or scratch built detection system?

Post by Maciek Szymanski »

A parcel from Ukraine just arrived:


1CFB1229-5994-4E63-BE87-FB0621BFB79F.jpeg
This is the infamous HE3 corona counter SNM-13. Anyway I want to try to tame the beast. And here I'have a question regarding the measurement system. I have two options. I can have a CAMAC crate with the PSU and some modules (for the neutron counting specifically: filter - amplifier and two types of discriminators). These are purely analog modules not using the CAMAC bus in fact just the supply voltages and mechanical interface. To complete the system I will need a HV bias supply, preamplifier and a pulse counter. This seems an easy path. For the start I even have a separate HV supply (not a CAMAC module).
As the other option I'm considering building the system from scratch with vacuum tubes. This will be more labour, but I will understand the system better, and with 250V anode voltage it should be much less sensitive to EM noise. And I can pack it into a single compact case (expect the preamplifier) instead of this huge and heavy and mostly empty CAMAC crate.

What are your opinions?
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland
ChristofferBraestrup
Posts: 131
Joined: Sat Apr 11, 2020 9:47 am
Real name: Christoffer Braestrup

Re: CAMAC or scratch built detection system?

Post by ChristofferBraestrup »

Escaping tubes in high energy/nuclear physics took a long time, since early transistor circuits were way worse than late tube circuts. There were even early NIM modules that were tube based (hence the 200V pin in the NIM bus!)

However the very well funded and extensive development in the 1960's and 1970's spearheaded by the national labs; Los Alamos, Brookhaven and especially Oak Ridge and the breakout companies thereoff (EG&G, Ortec, Tennelec, Nuclear Data), has brought the science so far along as it can really get for analog signal processing.

I think it's safe to say that you won't get a better nuclear data processing system than a proffessional CAMAC setup - however doing these projects should also be enjoyable, and you can definitely get any homebrew system "good enough".

Personally I would go the CAMAC route first, and then when I had a "known good" system then I would recreate the behavior with my own designs.

Both would be very interesting to follow along! Not enough info on CAMAC stuff in this community! or tubes, for that matter
ChristofferBraestrup
Posts: 131
Joined: Sat Apr 11, 2020 9:47 am
Real name: Christoffer Braestrup

Re: CAMAC or scratch built detection system?

Post by ChristofferBraestrup »

I guess it mainly comes down to the fact that there's two hats one can put on in these projects. The engineer cap and the physicist cap. If the design itself is the goal then whatever design the designer deems best the ideal solution. But if you have your physics cap on and want to produce the best experimental data to strengthen the credibility of your results then the only right thing is to go with the objectively better instrumentation, and for reproducibility you can't beat a commercial and well tested product!
User avatar
Finn Hammer
Posts: 298
Joined: Sat Mar 05, 2016 7:21 am
Real name: Finn Hammer
Contact:

Re: CAMAC or scratch built detection system?

Post by Finn Hammer »

Maciek,

From you, sir, I expect nothing less than a vacuum tube based detector/discriminator system with a nixie tube readout.

Cheers, Finn Hammer
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: CAMAC or scratch built detection system?

Post by Richard Hull »

Finn did a great tongue in cheek, but I have always liked to build my own stuff and go through the tortuous process of learning first hand the pitfalls and issues. Once at the successful end of the journey you own the process in a singularly unique manner. It is a matter of choice, as noted. Based on NIM or CAMAC use, where bias supplies abound and windowed spectro-amps are common, only the well designed preamp placed right at the detector head is typically problematic, not only in design and noise, but in matching to a tube. If you have a suitable supply and a CAMAC windowed spectro amp, use them!

The Corona tube can be a deceiver in the wrong hands. It is known to take a careful electronic hand to bias it and recognize noise from detected signal. All the best no matter what road you take.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Mark Rowley
Posts: 909
Joined: Sun Dec 29, 2002 12:20 am
Real name: Mark Rowley
Location: Sacramento California
Contact:

Re: CAMAC or scratch built detection system?

Post by Mark Rowley »

I expect this to be a challenging project regarding noise discrimination. You’ve probably read my previous post about Soviet 3He tubes. To recap, they are notorious for going nutty when exposed to the HV electrical noise of a Fusor. From my experience, they also seem susceptible to X-ray interference. Static neutron sources like AmBe/PoBe they perform beautifully.

I’d contend that such a tube will require a BTI dosimeter to ensure and confirm counting accuracy.

Looking forward to your results.

Mark Rowley
User avatar
Maciek Szymanski
Posts: 193
Joined: Wed Nov 20, 2019 2:31 pm
Real name: Maciek Szymański
Location: Warsaw, Poland

Re: CAMAC or scratch built detection system?

Post by Maciek Szymanski »

Finn, I'm afraid you have catched me. A tube based nixie driver would be something. But I rather thought abut a decatron and electromechanical counter in the lines of the DP-100 decade counting unit:


9236BFF9-CA1F-440C-AAEF-2604ED6E27C4.jpeg
I really like the look of the needle MES-54 counter (the thing looking like a stopwatch left to the block of the counting neon lamps). For other hand one can drive the the nixies with the dekatrons, so the circuitry will be not that complicaded.

Yes I've read about all the troubles of the corona tubes. But I like the idea of the high gas amplification over the weak signal amplifier. And I home that ability of reading the Russian language publications may help me in taking this challenge so I will try anyway. i thin for the start I will build the amplifier power supply and the preamplifier and check how it responds tho the EM noise with oscilloscope. Then we will see.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland
User avatar
Finn Hammer
Posts: 298
Joined: Sat Mar 05, 2016 7:21 am
Real name: Finn Hammer
Contact:

Re: CAMAC or scratch built detection system?

Post by Finn Hammer »

Maciek,

Understanding Russian is a great advantage, congratulations to that.
I own a variety of these russian tubes, and have done a bit of work trying to home in on the response to cosmic neutrons visiting my lab.
For a while I thought I was doing great results, as shown on the scope shot here, where the cyan trace shows signal at tube, yellow is signal after amplifier.

Scope shot of a rogue cosmic. Or???
Scope shot of a rogue cosmic. Or???

Then I noticed, that these great neutron counts happened when I got off my chair! Yes, my polyester pants against goat skin seat apparently created enough static to trigger the event.

This sent me back to squat, and I will not fiddle with these russian tubes untill I have a probable neutron source, for example 30kV @ 5-10mA with some deuterium in the plasma.

Then we will see.

Cheers, Finn Hammer
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: CAMAC or scratch built detection system?

Post by Richard Hull »

Sounds like you have a hair trigger, corona to pulse electrometer there!! I am reminded of the early GM tubes using air or reduced air pressure with no noble gas and no quench agent. 100meg resistors were needed to quench and count rates were in the 1000 cpm range max.

The Russian tubes are taken to the ragged edge of firing just like a GM tube, but they rely on corona to set up the tube and a quench agent to stop the sharp discharge. They are obviously of a special design and are in need of a critical bias and damping resistor. Apparently they are also electrostatically pulse sensitive to rapid external field changes. (static discharge) Good luck with making these insensitive to rapid external field changes.

I would try and electrostatically shield these tubes in some fashion. I know we think and perhaps rightly so that the grounded tube body obviates ESI but that may be an illusion if the tube is to be critically balanced in corona mode. These are special tubes supposedly designed to detect neutrons in a stressed corona mode. There is nothing wrong with a good heavy shield around these Corona tubes as neutrons will zip right through the shield assembly. A heavy shield will warrant against alpha beta rays as well. It appears that gamma and ESI are the culprits to be avoided in and around these tubes.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Post Reply

Return to “Neutrons, Radiation, and Detection (& FAQs)”