vacuum and high voltage

The "sputtered" gunk is actually burned oil vapor from the vacuum- Been there, done that

@bobhaha:

Also, would you be able to take a pic of your flyback? I'm quite interested in making one my self!

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Sorry, it took some time, but here you are:







The circiut is very simple. A TL494 oscillator for generating a squarewave with adjustable frequency and duty cycle. Then comes an ICL7667 mosfet driver and for driving the flyback there is a single mosfet-stage with an IRF640. With an input of about 12V there's an ouput voltage of about 20kV, but with very luttle current, so the voltage breaks down to the actual tube voltage, which was in my case between 1kV and about 3kV.

@pullbangdead:
Thank you for the explanation. Very interesting setup! I've never seen such a high voltage discharge before.

Best regards
argon

Nice looking plasma projects!

I like your electron tree too. ;-)

Dear millirad

Thank you very much for having a look at my simple page :beer: It's amazing, how many laserfreaks also have an interest in high voltage stuff. Thanks!

Best regards
argon

The shift from blue-violet to white as the pressure goes down is the vapor pressure from the pump oil. You might try a cold trap between the pump and the tube. (ice, dry ice, dry ice + acetone)

Steve

Hello Steve

Thank you for your explanation. This sounds plausible. Unfortunately my pump has also the problem that sometimes it spills back some oil to the discharge tube when turning off, so there's almost at any time some oil remaining in the discharge tube. It will presumably not be an easy task to avoid this.

Regards
argon

Argon, maybe the oil spill can be avoided. Add a vacuum valve to the atmosphere that you open before turning off the pump. This way the inlet is already at some pressure so the oil won't vaporize and enter the system, or at least it won't jump as easy into the system.
If you want to keep the system at a vacuum with the pump turned off, add an extra vacuum valve just before the system.

Bluefan said:

Argon, maybe the oil spill can be avoided. Add a vacuum valve to the atmosphere that you open before turning off the pump. This way the inlet is already at some pressure so the oil won't vaporize and enter the system, or at least it won't jump as easy into the system.
If you want to keep the system at a vacuum with the pump turned off, add an extra vacuum valve just before the system.

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A valve won't prevent backstreaming during operation if the pump backstreams while the system is in molecular flow instead of laminar flow. The line between laminar and molecular flows, below which oil can backstream if steps aren't taken to prevent it, is usually quoted as between 100 and 150 mTorr, ie .1 to .15 Torr.

It's pretty typical for a single mechanical pump to be able to reach pressures where oil can backstream from the pump. One thing you can do if you have a pressure gauge that's accurate is to install a needle valve that can be adjusted such that the pressure is constant, say at ~150 mTorr, just above the pressure at which oil would begin to backstream. This gives you a decent level of vacuum without any backstreaming and without much additional effort at all.

If you want lower pressures without backstreaming oil, then you need to take other measures.

HIGH VOLTAGE the only way to go

Thanks for sharing all...

Dear All,

Does anyone object if I use some of these images to encourage high school students along with their physics studies?

Best regards,

Matt

Oh man i love your pics ! I whish i had the skills to make something like this !

What camera did you used ?

@mlyle:
Of course you can use all of the pictures I posted there and every pic of my webpage as well (Hochspannung als Hobby). I'm happy if someone could use some of the material there

@jimdt7:
Thank you very much!

I whish i had the skills to make something like this !

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These experiments are easy to do. You don't need special skills for this. Just a little vacuum pump and flyback from an old computer monitor or TV as a high voltage source.

The cams are a very old Sony DSC-F505 and a (bit less old but rather cheap) Sony DSC-T50.

There are quite many sites in the internet explaining how it can be done :beer:

argon