What type of tubing / valves are used in vacuum and de-gassing, gas population experiments?

[Miles Thatch]

I'm looking to experiment with making a cold cathode character display. I have plenty of experience experimenting with manufactured IN-12 tubes and the power supplies that drive these, but I want to step further to experiment in making my own.

What grade of materials / tubing / valves should I be looking at to try and build my own jig for evacuating air from a tube and populating a gas?

I don't suppose just about any valve with do (like liquid control valve) and looking at my hobbyist grade vacuum chamber, the tubing contains a spooled wire on the inside to provide rigidity to counter the vacuum forces.

Would brass / copper tubing sealed with aluminum weld be suitable?

[gregebert]

I did a lot of research about 15 years ago when I was thinking about doing neon art. There are 3 really good books (The Neon Engineer's Notebook, Neon Techniques, and The Neon Superguide) and I recommend you read all 3 cover-to-cover. Though not particularly for nixies, there is a lot of good info about the overall process. I have yet to read the Weston text (Cold Cathode Glow Discharge Tubes).

You will need to pump down to the micron range, and that generally requires a diffusion pump ( a fascinating device, and another topic on it's own...) in addition to a traditional vane pump that will get you well-below the millibar range. I decided against doing neon art because the bombarding process is very dangerous; far more dangerous than experimenting with microwave oven transformers.

The manifolds I saw were made of glass, even the valves, and require a special lubricant/sealant. I think you can use induction heating, rather than bombarding, for removing impurities. The other thing that discouraged me was the need to use mercury; it's rather toxic and I was concerned about inhaling vapors. I'm not afraid of mercury in liquid form.

Keep me posted if you start experimenting. I have a vacuum pump and intend to do some basic tinkering with gas discharges, but I have no intention of taking it to the point of making something durable.

[Miles Thatch]

Thanks for the read references. I know this group has a shared drive with some reading material. Maybe I can find some of these there. 

I'm primarily interested in making a few special character display nixies like the in-12 tubes. More experimentation than anything. I've seen a gent on Youtube make one in his garage.  

[Miles Thatch]

Actually there was something else I was wondering about. 

Is there such a thing as an accurate vacuum gauge which you can just drop into a chamber instead of connecting to the valve / air line of the pump? Conceivably it's something that has it's own sealed air container and would detect the expansion force / difference between external and internal pressures? 

[liam bartosiewicz]

I’ve read somewhere that people have had reasonable success in making Nixie tubes with just a dual stage rotary vane pump, so it may be worth giving that a shot before spending loads of money on a diffusion/turbomolecular pump, controller and pirrani/ionization gauges. Check out this website here: 

On Aug 28, 2023, at 10:56 AM, gregebert <greg...@hotmail.com> wrote:

I did a lot of research about 15 years ago when I was thinking about doing neon art. There are 3 really good books (The Neon Engineer's Notebook, Neon Techniques, and The Neon Superguide) and I recommend you read all 3 cover-to-cover. Though not particularly for nixies, there is a lot of good info about the overall process. I have yet to read the Weston text (Cold Cathode Glow Discharge Tubes).

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[gregebert]

The only gauge I can think of would be a standard "U" gauge (manometer), but that is only practical down to a few millibars with mercury. Maybe there are some exotic liquids with low vapor pressure that might work a bit lower, but I doubt anything exists that would get you into the micron range.

For vacuum levels into the micron range, you need something like a Pirani gauge, and that requires external connections.

[Mac Doktor]

On Aug 28, 2023, at 1:56 PM, gregebert <greg...@hotmail.com> wrote:

I did a lot of research about 15 years ago when I was thinking about doing neon art. There are 3 really good books (The Neon Engineer's Notebook, Neon Techniques, and The Neon Superguide) and I recommend you read all 3 cover-to-cover. Though not particularly for nixies, there is a lot of good info about the overall process. I have yet to read the Weston text (Cold Cathode Glow Discharge Tubes).

I went to neon school back in 2001. I have all of the books that were in print them plus two thick binders of photocopied articles from all over the place. Naturally, I can't get to any of it right now.

I decided against doing neon art because the bombarding process is very dangerous; far more dangerous than experimenting with microwave oven transformers.

It has to all be set up the "right way". Anything less is asking for disaster. If you don't feel safe don't do it.

The manifolds I saw were made of glass, even the valves, and require a special lubricant/sealant.

Yeah, borosilicate. A vast improvement over metal manifolds. The thing is that for ages neon was entirely an art form. Processing was done by the seat of the pants. At the turn of the millennium more scientific, documented methods were coming online and replacing the guesswork with actual physics. This involved the use of more apparatus.

I think you can use induction heating, rather than bombarding, for removing impurities.

We certainly didn't have anything like that then. Probably way more convenient, too.

The other thing that discouraged me was the need to use mercury; it's rather toxic and I was concerned about inhaling vapors. I'm not afraid of mercury in liquid form.

The amount of mercury is pretty small. In the case of a broken tube, air the room out. It's no worse than breaking a large fluorescent tube.

Terry Bowman, KA4HJH
"The Mac Doctor"

https://www.astarcloseup.com

"Would you like to see the relevant data?"—343 Guilty Spark, Halo 2