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Vacuum for high voltage plasma

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Toasty

Wed Feb 10 2016, 08:59PM

Registered Member #56785 Joined: Fri Aug 28 2015, 02:54PM
Location:
Posts: 20

Hi all
I plan on making a vacuum chamber for simple plasma expiriments. The only thing i still need is a good vacuum pump. I have seen people use refrigerator compressor, modified air compressor and a simple modified bicycle pump. I am currently thinking about using the modified bicycle pump since i don't have an air compressor laying around. Does anybody here have some experience with those? Will it make a good vacuum?
Thanks for helping me out

woodchuck

Wed Feb 10 2016, 11:34PM

Registered Member #39190 Joined: Sat Oct 26 2013, 09:15AM
Location: Boise National Forest
Posts: 65

My first vacuum pump was a section of surgical rubber tubing and two print rollers. Sort of a manual peristaltic pump. It helps if you put a tiny amount of a low vapor pressure oil on the inside of the tubing (like the oil used in diffusion pumps).

It's slow, but it is more effective than you might imagine.

LouisHV

Thu Feb 11 2016, 02:16PM

Registered Member #55102 Joined: Tue May 26 2015, 12:03PM
Location: Johannesburg, South Africa
Posts: 4

Hi Toasty,

I have used a refrigeration compressor from a fridge I found in a dumpster on the street I live in. It doesn't hold a candle to my Edwards RV5 but it got me into "playful" plasma territory really cheap. Be careful of the stuff inside the copper pipes... disposal regulations and not to mention what it could mean for your health. Someone with more experience will hopefully chime in on this subject.

From experimentation I found fridge compressor > tyre compressor.

The bicycle pump... I once tried to pump down a jam jar (metal lid) with a "reversible"bicycle pump. It worked but it leaked through the cheap seals within a minute or so. The type of bicycle pump that has a foot pedal type of actuator works really good, if you can use an average quality one way valve inline.

If you are willing to spend some money...

this: http://www.amazon.com/Tenive-Double-Rotary-Economy-Vacuum/dp/B017AYO82E/ref=sr_1_2?ie=UTF8&qid=1455198581&sr=8-2-spons&keywords=vacuum+pump&psc=1 is not bad at all! I can not vouch for the quality though.

for less than half the price http://www.amazon.com/Zeny%C2%AE-Single-Stage-Rotary-Vacuum-R410a/dp/B012CFTYX4/ref=sr_1_3?ie=UTF8&qid=1455198581&sr=8-3&keywords=vacuum+pump will get you to a claimed 5 Pascals.. probably much higher pressure than that but hey for 35 USD + shipping... Plasma all day long!

If you are willing to spend a 100USD or so a 2nd hand yellow jacket vacuum pump built for HVAC servicing will last long, be serviceable, have parts and oil available and is reputable and known in the industry.

If you are desperate to play with plasma, I once jammed a nail into the tip of a big-ish plastic syringe and pulled back on the plunger, touched the nail to a small flyback used to power a bad quality plasma ball toy (+-5kv maybe) and got some great quick and cheap plasma goodness. Used some hot glue to seal the nail to tip part and if careful enough to not pull the plunger out completely could use it quite a couple of times.

Good luck and peace :)

Louis.

edit: I like woodchuck's method. with an okay one-way valve and nice silicone rubber hose it should work surprisingly well.

2Spoons

Thu Feb 11 2016, 11:41PM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615

If you want a really simple solution you could make a venturi pump, also known as a water aspirator. I made one when I was about 14, out of some bits of copper tubing. Worked a treat for plasma-in-a-jar experiments. Just have to be careful not to let water get sucked back into the jar when turning off the water supply.

How good your vacuum is depends on how cold your water supply is (colder=better).

Hazmatt_(The Underdog)

Fri Feb 12 2016, 02:28AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

I made an aspirator too, it worked pretty well, but I think buying one for the $14 would be more do-able.

I would recommend to stay away from the really nice pumps on ebay because they always need a rebuild.
I still have yet to successfully rebuild my Welch 1402 because the main seal just listed as "seal" in the drawing has a trick to install it, AND when rebuilding the pump you actually have to repaint it. The painting process serves to seal the pump partially, so they are tricky bastards to rebuild, much more so then what appears on the surface.

A major rebuild kit for a simple Welch is gonna run $250, in addition to the pump running $150, but you're going to need a Hastings gauge as well to see if you rebuilt it right, which is going to run another $250 for the meter and tube.
And if you didn't rebuild it tight enough, you might have to spend $45 on heavier oil to get you where you want to be, half a micron.

So I would stick to the aspirator for now.

P.S. don't even get started on vacuum line! that stuff is really expensive too!

Ash Small

Fri Feb 12 2016, 02:35AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Have you looked on eBay?depending on what side of the pond you're on it's either Edwards or Welch, I think.

Thet are surprisingly cheap, and even when the buyer puts 'untested' or whatever, the chances are they are still perfectly servicable.

There are tutorials online for rebuilding them cheaply if required.

It's sensible to change the oil.

I've two I paid next to nothing for.

Diffusion pumps come up cheaply as well, but you won't need one of those yet

2Spoons

Fri Feb 12 2016, 03:01AM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615

Sometimes I forget how easy it is to just buy stuff from ebay. I made my aspirator before the internet existed. Buying one was just not an option. And frankly, building one and seeing it work was very satisfying.

woodchuck

Fri Feb 12 2016, 04:25AM

Registered Member #39190 Joined: Sat Oct 26 2013, 09:15AM
Location: Boise National Forest
Posts: 65

FWIW, of the many varied water aspirator pumps out there, the best I know of is the polypropylene Thermo Scientific Nalgene pump. It produced the best vacuum and used the least amount of water.

jpsmith123

Fri Feb 12 2016, 04:46AM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

Hello LouisHV,

I'm wondering, do you have any experience with that "Tenive" vacuum pump?

The reason I ask is because on the amazon web site, the ultimate vacuum spec. is stated to be 0.3 Pa, which is very good for a cheap AC service type vacuum pump.

If that pump will actually go that low I want one (although it would be better if it also had a gas ballast feature).

LouisHV wrote ...

<snip>

this: http://www.amazon.com/Tenive-Double-Rotary-Economy-Vacuum/dp/B017AYO82E/ref=sr_1_2?ie=UTF8&qid=1455198581&sr=8-2-spons&keywords=vacuum+pump&psc=1 is not bad at all! I can not vouch for the quality though.

<snip>

Toasty

Fri Feb 12 2016, 05:57AM

Registered Member #56785 Joined: Fri Aug 28 2015, 02:54PM
Location:
Posts: 20

2Spoons wrote ...

If you want a really simple solution you could make a venturi pump, also known as a water aspirator. I made one when I was about 14, out of some bits of copper tubing. Worked a treat for plasma-in-a-jar experiments. Just have to be careful not to let water get sucked back into the jar when turning off the water supply.

How good your vacuum is depends on how cold your water supply is (colder=better).

Oh nice! Never heard of it but it looks like a simple way to get a nice vacuum
Thanks

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