vacuum and high voltage

Hi guys out there

My second hobby are experiments with high voltage stuff (tesla coils and a lot of other hv-stuff). I would like to show you some of my vacuum high voltage experiments I made in the last few weeks.

With the following vacuum pump and a very simple high voltage generator (flyback) it is possible to perform some interesting discharge pictures.

This is the pump from ebay. It does a vacuum of about 0.05mbar under optimal conditions.



An evacuated glass bottle at relatively high pressure (bad vacuum):



A bit better vacuum:



A selfmade discharge tube (glass):



Firing up at different pressures:











After a while of using this tube, the cathode sputtered some metal vapor to the surface of the glass tube:



And another selfmade discharge tube, now a bit longer (50cm):



Thanks for looking up the thread If you are intersted in more HV-stuff, you could also visit my page www.hochspannung.ch.vu (german)

Best regards
argon

Mmmm, plasma....

Here's the dielectric-barrier discharge system I used in my undergrad lab. It was pretty big, and when our big power supply was working, we could put a really big gap in there. I think the plates shown are like a 6-inch diameter?

Oh, and this discharge pictured is at atmospheric pressure, not under vacuum.

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ETA: Are you sure in that one picture of the discoloration, it was "sputtering" from the cathode?

:drool: the last picture...

That's pretty cool that you were able to get nice discharges like that with a single stage refrigeration vacuum pump, I've been wanting to try something similar with making actual sealed glass discharge tubes.

I bought some glass tubing on ebay but it was too small to seal the electrodes and still have a port to evacuate the air from, I think I should order some bigger tubing and try again

Thanks ;-)

Oh, and this discharge pictured is at atmospheric pressure, not under vacuum.

Click to expand...

What is it actually?

ETA: Are you sure in that one picture of the discoloration, it was "sputtering" from the cathode?

Click to expand...

Yes, I think so. The metal surface on the glass could just be removed by acid (salt acid in my case).

Some more pictures of the 50cm Tube:





Deflection with a magnet from a Magnetron:





Cathode light:



EDIT @MarioMaster:
Sealed tubes would even be cooler! Unfortunately it is not an easy task to seal a tube and to bring in the electrodes... I think I could not make it working

Best regards
argon

You could be generating soft x-ray with those arcs. Old neon benders found out the hard way.

HMike

Hemlock_Mike said:

You could be generating soft x-ray with those arcs. Old neon benders found out the hard way.

HMike

Click to expand...

Thanks Mike I'll have to keep that in mind - my CDV-700 geiger counter should be able to pick up soft x-rays (I think)

I don't think this tube generates x-rays, because the voltage across the tube when it has fired is just 1.5 kV and the pressure is too high. For generating x-rays you should have more than 20 kV anode voltage. Every big transmitting tube has a much higher anode voltage than 1.5kV and a better vacuum but still doesn't emit x-rays.

Regards
argon

Awesome pics, argon!

You should see if you can source some cheap inert gases. Argon gives off a soft purple light, like in the first discharge picture. It's quite pretty.

Anyone has an idea why the light has athisperiodic pattern in the length of the discharge?

GREAT STRIATION PATTERNS!!! What pressure in atmospheres is that 50cm one running at?

I remember my physics teacher showing us this but nothing this beautiful was achieved.

BTW yes, soft x-rays are most definatly being produced here... you can get some pretty cheap x-ray sensitive film and developer kit from places on the internet... expose your hand to it, with the film behind it, for around a min, and I guarantee you will see a result.

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

Thanks!

argon said:

Thanks ;-)


What is it actually?


Yes, I think so. The metal surface on the glass could just be removed by acid (salt acid in my case).

Click to expand...

Yeah, I suppose you're right about a bit of sputtering. The whole time I worked on glow discharges was at atmospheric pressure, and I sometimes slip into forgetting the other things that can happen when you working at low vacuum instead of no vacuum.

As far as your other question, I'm not sure I follow. Are you asking what my picture was?

Bluefan said:

Anyone has an idea why the light has athisperiodic pattern in the length of the discharge?

Click to expand...

It's complicated.

I'm going to go with saying "plasma dynamics". Local variations in plasma/gas parameters.

Very cool stuff Argon. I've been reading up a lot on it lately and I'm going to try and build a demonstration Farnsworth Fusor for my senior project this year. Have you ever tried to make one before?

--Hydro15

@MoonShadow:
Thank you!

You should see if you can source some cheap inert gases. Argon gives off a soft purple light, like in the first discharge picture. It's quite pretty.

Click to expand...

Indeed, that would be interesting! Maybe I will try to do that.

@bobhaha:
Thank you as well.

What pressure in atmospheres is that 50cm one running at?

Click to expand...

That's a good question. The pressure is about 0.1mbar I think, maybe even a bit less (I've no manometer for measuring the actual pressure). This would be about 9.869E-5 atm if I'm right.

BTW yes, soft x-rays are most definatly being produced here...

Click to expand...

Why do you suppose that? In my opinion it is not possible to generate x-rays with such a low anode voltage (only 1500V!). Think about it: X-rays are produced, when high accelerated electrons hit the anode. To fulfill this, the anode voltage must be high enough to accelerate the electrons enough, but with 1500V this is impossible. And there's another reason too: On their way to the anode, the electrons are colliding with air partikels, that is why the light is emitted. With every collision the electrons are slowed down. This is because the vacuum is not good enough, so there are too many gas particels still there. If the vacuum would be better (2 stage pump), the voltage across the tube would rise and at about 15 to 20kV it would start to produce x-rays.

If this tube would produce x-rays at a voltage level of 1500V, believe me, every backlight tube of a flat screen and every FL-lamp of a scanner would produce x-rays too.

@pullbangdead:

As far as your other question, I'm not sure I follow. Are you asking what my picture was?

Click to expand...

Yep Unfortunalety my English skills are not very good.

@hydrogenman15:
Thank you very much.

I'm going to try and build a demonstration Farnsworth Fusor for my senior project this year. Have you ever tried to make one before?

Click to expand...

No, absolutely not :yabbem: I think I would not be able to build a fusor myself. And for this, you need special equipment too. No way for me at the moment... but if you really do this, then please provide some documentation, maybe here or in a new thread. That would really be interesting!

Best regards 2 all
argon

@hydrogenman15:
Thank you very much.

Quote:
I'm going to try and build a demonstration Farnsworth Fusor for my senior project this year. Have you ever tried to make one before?


Quote from Argon:

No, absolutely not I think I would not be able to build a fusor myself. And for this, you need special equipment too. No way for me at the moment... but if you really do this, then please provide some documentation, maybe here or in a new thread. That would really be interesting!


I'm just planning on building a demo Fusor, so It's not going to actually do any fusion... Not the first one I'm building anyways.

--Hydro15

argon said:

@pullbangdead:

Yep Unfortunalety my English skills are not very good.

Click to expand...

No problem, your English is very good overall.

My picture is a an atmospheric-pressure glow discharge, similar to what you have in many ways, but also a bit different due to the different pressure regime. More specifically, it's a dielectric-barrier discharge, meaning there's a dielectric (quartz in this case) covering at least one of the electrodes (both in this case), with the electrodes in a parallel-plate configuration.

But it's running at full atmospheric pressure with the big electrodes and large gap. The gases are probably something like helium or a bit of neon thrown in IIRC, much lower breakdown voltage that way. With a big gap like in that picture (I think those electrodes were a 6-inch diameter?) it was really tough to break-down normal air, but throwing some inert gases in there helped a lot.