Russian Corona Tube - resistance

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Dennis P Brown
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Russian Corona Tube - resistance

Post by Dennis P Brown » Sat Nov 12, 2016 6:49 pm

Picked up a Russian Corona Tube - resistance was only 2.6 k-ohm across the HV connector and outer case! For a tube that needs 1950 volts min, that strikes me as a extremely low value of resistance. Is that normal or is the tube bad - the tube is over a foot long (13.5 inches) and has a glass tube (filled with?) inside a metal outer protective case. This tube only has a single end connector for the high voltage so I assume the outer case is meant to be grounded. Not sure my 20 ma max, +/- 5 k DC supply can handle that low of a resistance. Puzzled by this tubes resistance value.

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Re: Russian Corona Tube - resistance

Post by Rex Allers » Sat Nov 12, 2016 10:01 pm

I've got three Russian tubes here: CHMO-5, CHM 65, and CHM 32. I haven't tried to use any of them yet, but I just measured them with an ohm meter and they all show completely open. That's what I expected. Don't know what could be up with yours but it doesn't sound good.
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Richard Hull
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Re: Russian Corona Tube - resistance

Post by Richard Hull » Sun Nov 13, 2016 7:55 am

All detector tubes of the GM, or neutron tube type, (3He and BF3), absolutely must read infinity, a dead open to any ohmeter. No readable resistance of any sort is allowed or the tube is most definitely defective.

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.

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Dennis P Brown
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Re: Russian Corona Tube - resistance

Post by Dennis P Brown » Sun Nov 13, 2016 6:31 pm

Thanks all for the input; so, the tube is junk - great. Have been not batting well on neutron detection ...0 for 1000 so far. LOL. So, in short, for me - there is the hard way, wrong way, correct way but major problems, and finally, the way that really works (not necessarily the correct way.) I do all the ways but the last one, many times and only after a very long time, and even repeating the first three a few times, do I finally reach the last way. ugh.

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Re: Russian Corona Tube - resistance

Post by Steven Sesselmann » Fri Nov 18, 2016 8:03 am

Dennis,

It's a difficult path indeed, and only the chosen ones will make it ;)

How about trying a CHM-12 with one of my preamps, a relative painless solution.

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG

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Re: Russian Corona Tube - resistance

Post by prestonbarrows » Sat Nov 19, 2016 5:02 am

As usual, Richard et al. have covered this, but the Russian surplus He3 tubes are typically of the 'Geiger Muller' type. This consists of a central fine signal wire located co-axially in a grounded cylinder with a reactive atmosphere between. The 'signal' is connected to the central wire which should be completely isolated from the grounded can on the benchtop.

Under normal conditions, a high voltage of ~500-1000V is applied between the central wire and co-axial can. When not in the presence of any ionizing radiation, the central signal wire should read infinite resistance to the grounded can.

When a particle to be detected passes through the detector, it leaves a track of ionized secondary particles which temporarily electrically bridge the gap between the central wire and grounded can. Since an external bias voltage is being applied, this results in a short current pulse. This event can be seen with a probe capacitively coupled to the high-voltage biased central wire directly on a scope, or more informatively with a NIM BIM setup to measure the rate of such events.

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Dennis P Brown
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Re: Russian Corona Tube - resistance

Post by Dennis P Brown » Sat Nov 26, 2016 4:59 pm

Well, looks to be a ground loop caused a mis-reading on the Russian tube (it now reads off-scale even for mega-ohm as it should once I removed it from the circuit); I am usually careful and catch such mistakes but this time I designed one into my circuit ...lol. My detector system can handle only 1.5 kV but the Russian tube requires 2.0 kV or more. So I supply 2.2 kV HV to the detector tube (the supply can go to 6 kV @100 ma) and I used a voltage divider to reduce that voltage to a level my amp/counter system can tolerate (the 1.5 kV value.) However, that creates a direct ground - via the 2 k-Ohm resistor in the divider circuit - to the detector tube via its grounded outer shell.

So, I either need to let the tube float and keep the 1 mega-ohm res. feeding the HV into the tube (to prevent current runaway when it is ionized), or I guess I should put the detector tube directly to the 2.2 kV (by-pass the 1 mega-ohm resistor in the divider system) and instead, add a 1 mega-om resistor from detector tube's outer case to allow it to feed into ground (but still prevent a current runaway.) The later seems more likely to work; of course, I'd still have a ground loop in that the case on the detector tube would still be connect to the divider ground as well but it would be through a 1 meg ohm resistor this time. Without floating the detector case, really is no easy solution unless I build a battery supplied HV system ...that isn't something I'd do unless there is no other method that works - I've built a 25 kV HV system that uses a 6 volt battery but that just isn't fun and I am tried of side projects. These are eating up all my time rather than doing the fun part of getting fusion ...well, maybe. Until I detect them, neutrons don't exist ... .

Will consider the unit offered here but that has to wait till summer at the earliest - that is when my daughter finishes MIT and I'll have some funds available ...lol.

Minor aside: my fusor is either getting seasoned or I am because I can quickly get it stable at 25-26 kV and 30 - 50 ma anytime I want with a pressure of 5 - 8 microns deuterium. Now if I could just get the darn neutron detector system working ... . I can push the supply to 28 kV but that is more work and not as stable so, unless needed, will stick to the 25/26 kV level.

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Re: Russian Corona Tube - resistance

Post by Richard Hull » Sat Nov 26, 2016 10:29 pm

Probably a bit of conditioning for both you and the chamber. Actual operation is the best classroom for controlling a fusor.

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
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Re: Russian Corona Tube - resistance

Post by Rex Allers » Sun Nov 27, 2016 7:40 am

Dennis,

Good to learn your tube isn't bad but I'm struggling to follow the circuitry you are trying to use. If you have a divider that's putting 2 k ohms across the tube, I don't see any way it can possibly work. First, I don't see the purpose of the divider, but if it is putting 2K across the tube at 1500 V that 2K will draw 1100 watts! Actually, you'll never get the required voltage on the tube.

Richard posted a nice pdf article about using the Russian corona tubes (I think in Aug 2016 and now in the FAQ sections somewhere). Here is a block diagram from that paper.
Corona block.png
The capacitor shown blocks the DC from the tube to the amp but allows the pulses from discharges in the tube to get to the amp. It could be necessary to have some kind of limiting on the amp input to prevent really big spikes from killing the amp, but I see no reason why you need a divider.
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Dennis P Brown
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Re: Russian Corona Tube - resistance

Post by Dennis P Brown » Sun Nov 27, 2016 7:00 pm

You are correct - again, I wasn't paying attention to what needed to be done but I was just thinking what voltage I wanted ...bad move.

I will have to use a battery supply as you show in your diagram; I realize that after testing my current supply.

Far too much noise by the fusor using a common grounding system ... . I really hate secondary projects and it looks that every system I have built - fusor power supply, fusor chamber, gas supply and even minor physical support systems all grow into far more complex systems then I had at first expected.

Guess it makes perfect sense for this neutron detector system to have the same issues. Luckily, I have a very small 2 kV AC supply that uses a 12 volt battery. I have diodes and can build the metal box to hold everything - all cables and connectors will be co-axial so I hope this reduces noise; if I go over board, I guess I can enclose the detect tube, as well.

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