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ArcticMyst Security by Avery

Fun with 770V

Tech_Junkie

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Cool. I'm going to drill a hole in a skull I have, and put the tube on top. So it looks like its having and idea.

lightb3.jpg
 





Sigurthr

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Depending on the xenon pressure you could also apply HV between the Anode and Cathode with an unheated filament and get a xenon discharge spectrum.
 
Sigurthr

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It depends on the arc length and the gas pressure. I would estimate that 10kV and a couple pA would be enough to get a faint glow. 20kV and maybe 100uA would give a decent arc unless the pressure is fairly high, then you might need maybe 400uA.
 
Hiemal

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I wouldn't go above pA, because then you run the risk of X-ray hazards. There's a reason HV rectifiers in old tube tellies have those metal boxes on them and even have warnings stating "X-ray hazard". :p
 
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Sigurthr

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I wouldn't worry about xray below 20kV though, the glass envelope will stop most of it, especially on the tubes with thicker glass. That's why coolidge tubes use a special low density/thin section of the envelope. Upping the voltage beyond 20kV is when you have to start to worry about how many pA (or uA or mA) you're putting out, hehe.

All that aside... you won't get ANY xray out of an inert gas filled tube, only tubes with a true vaccuum will produce Xrays. The gas mollecules get struck with the electrons which ionize them in a gas filled tube instead of the electrons flying into the anode/glass and causing Bremsstrahlung, which is the real source of the Xrays from tubes.
 
Sigurthr

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Yeah that'l work, but it may burn out your cathode if you don't rectify the NST output or get a high power HV resistor to limit the current. 12KV ~ >30mA is a LOT of juice for a cathode that isn't meant for that kind of punishment. I have a 24kV rectifier which can withstand 24kV of AC, but a 10kV rectifier like yours can't handle 12kV of AC without hefty current limitation.
 
Hiemal

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Sig, if he never plans on using the tube for rectifying, why would it matter anyway out of curiousity? Or would it come down to heat dissipation on the cathode and preventing failure of the tube completely?
 
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Sigurthr

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Le Quack said:
Or would it come down to heat dissipation on the cathode and preventing failure of the tube completely?
Click to expand...

Exactly! The cathode normally doesn't have to bear much stress compared to the anode, but when you overvolt a valve rectifier with plenty of current you can get cathode ablation.
 
Tech_Junkie

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I really hate the fact I cant absorb this knowledge. I'm far from stupid. But the older I get, the more my brain softens. And its going quick.

When I got my first library card when I was young, the first two books I picked up where art, and electronics. I liked art better and never really turned back. I'm really good at taking apart, and putting back together anything. But when you start adding values, stats, ect to the equation I'm lost.
 
Seoul_lasers

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Sigurthr said:
Depending on the xenon pressure you could also apply HV between the Anode and Cathode with an unheated filament and get a xenon discharge spectrum.
Click to expand...

Or get soft X-rays. Personally I'd not exceed 25Kv with any of these tubes.
There has been several cases of some of these tubes creating some very decent X-ray exposures due to the low pressures inside the tubes and the Anode/cathode configuration.

Also, another side note is that some of the larger tubes contain significant amounts of Thorium, Cs137 and some even contain Co60
vacuum tubes « Special Nuclear Material

Again being Ex-Hazmat, our tubes were handled with EXTREME care. A couple of tubes needed a Pb shielded box. 500 Westinghouse 1B37 in one storage room= a very significant dose of Gamma Radiation.
 
Sigurthr

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500! Damn, heh, I have one transmitter spark gap tube with ~7uCi Ra226 in it and it is pretty hot.
 
Seoul_lasers

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Yup. That's at least 2mSv/hr with the door closed.
Dangerous enough that full lead lined gloves and apron
And respirator were needed when entering
The rad lockup. Doseimeter not optional
Even outside the facility.

We split the lockup tubes and had them build a second
Storage due to the unsafe levels.
CNRC eventually sent someone to take them off our hands.
We were a disposal for ITAR items not a nuclear waste unit.
 
Sigurthr

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That makse sense then, I was wondering why anyone would purposely store them in such a high density.

How much of it was Th? Ra, Co, and Cs gammas are easy to stop with apron and gloves, but those high energy Thorium gammas are pretty penetrating.
 
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