Always Wrong!
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
pmin = (1/d)*exp(1-b) where b is a gas-dependent constant
As the page says, you can get this by differentiating Paschen's law
V = (a * d * p)/(b + ln(d*p)) wrt p, which gives you
(a*d)/(b + ln(d*p)) - (a*d)/(b + log(d*p))^2
and setting the derivative to zero to find a min (or max).
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
I think he's been "funning" us all. No one can be that wrong without working at it. I think AW deliberately misstates the facts to get a rise out of us! Being consistently wrong takes more brains than just using guess-work. A deliberate > 50% wrong score indicates considerable intelligence. ;-)
-- VWW
No shit, asshole.
That what you get for the "Um".
The initial arc in a pure vacuum is hard to initiate. The moment it is, however, the node that was struck by the electron stream gives off metallic vapors.
The circumstance of your "vacuum" and the entire chamber at that point is now 100% different than the starting set-up.
Yes, the thought did occur to me. He was just slightly too obvious in that last troll, but just enough to work (on a weekend).
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
I worked on the development of an HV oil filtration device. It used our
20 kV supply, and our plate arrangement and our tank chamber and oil pump. We PULLED the oil through the chamber and filter media as this reduced the pressure in the chamber and that was enough to keep arcing events from happening. Operated with the lid off, it would arc immediately. With the lid on, the pressure would pull down almost immediately as the oil's viscosity took some work to pull it through the piping. That reduced chamber pressure kept it from arcing.Your curve is for pressures well below that.
In normal air, the voltage required to establish an arc rises as pressure drops. This is NOT data related to a vacuum. It is for reduced pressure environments.
The curve plot refers to vacuums and very low pressures.
Here's the Paschen curve extended all the way to atmospheric pressure.
and again
Wrong Again.
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Then the tanks in our design were pulling below 1mm and were on the other side of the slope.
Either way, the result was that it did not arc when under negative pressure, and did arc in open air.
This refers to the tops of the plates in the filter chamber, which was bigger than a gallon,but smaller than a cubic foot.
A good question would be to see what the plot is on values above sea level. IOW, what kind of insulator is compressed air?
The curve I linked to (air, 0.1" gap) plots from 760 torr (which is 1 atmosphere, of course) downward, and the breakdown voltage of at 0.1" gap in air decreases with dropping pressure down to about 0.2 torr, which is a medium vacuum. For to go up, the gap size would have to be < 1 micron.
High voltage clearances should be increased for devices that have to remain functional at high altitudes.
Many, many years ago I worked with a suitcase-sized system that contained a subminiature Van de Graff generator enclosed in a pressurized SF6 atmosphere. It made many hundreds of kV, IIRC. AFAIUI, SF6 will likely be banned if they can find a workable alternative- it's a very effective greenhouse gas.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
"The Journey is the reward"
eff.com
thanks. will enter as an octave function.
Other wise know as plasma.
Hmm. Think about FS6, roughing and defusing pumps. Of course, it's nice to have an ion gauge and DOM's sitting in the chamber for safety shut downs.
Jamie
20kvolts? that's it?
Jamie
The superconductive cavities at the Jefferson Labs/CEBAF electron accelerator have unloaded Qs around 1e8, and run ultra-high vacuum inside. The electric field strength was approaching where ions are ripped right out of the metal surface, no gas needed. Of course, as you say, once that gets going, it's all over.
The next generation may be cavities fabbed from single-crystal niobium.
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
duced
"The Journey is the reward"
eff.com
I worked for a bit at an FEL with a section of 'SLAC' linear accelerator. The wave guide was filled with a few atmospheres (Can't recall any exact numbers) of SF6 to stop it from arcing over. Maybe Xenon would work.. but expensive!
George H.
Wrong.
really? Guess you don't know much then.
Jamie
The electron stream would be a plasma, idiot. The initial arc, which is what is referred to here is NOT. The metallic vapor is from the stream's impact, not part of the stream itself. Fuck off, dork.
I believe Dow Liquid Epoxy compound was used for 50kV into a vacuume system to make a 'custom' feedthru into e-8 to e-9 vacuum:
800 441 4369 517 832 1426 cig .AT. dow .DOT. com I do remember using polyimide PCB's with no problem and someoneonce 'tried' to use polyamide material causing great problem.
I believe Dow Liquid Epoxy compound was used for 50kV into a vacuume system to make a 'custom' feedthru into e-8 to e-9 vacuum:
800 441 4369 517 832 1426 cig .AT. dow .DOT. com I do remember using polyimide PCB's with no problem and someoneonce 'tried' to use polyamide material causing great problem._______________________________________
Use a spark plug?
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