Vacuum pumps for evacuating DIY nixies?

[Miles Thatch]

Good day.

Since we require to reach vacuums of 10 - 50 torr depending on the gas mixture. What sort of vacuum pumps are we looking at sourcing to achieve those levels?

[Miles Thatch]

When searched I'm just getting standard degassing Vacuum Pumps for vacuum chambers:

I don't think these will get down to the required vacuum levels.

[Nick]

Look at Dalibor's videos.

[gregebert]

I think you mean 10-50 microns (which is 1000 timer lower), not 10-50 Torr. One atmosphere of pressure is 760 Torr (760mm Hg).

I've seen neon-sign texts stating the need to get below 1 micron for proper bombarding, and I imagine nixie tubes are similar.

[Tidak Ada]

Microns what? Liquid hydrogen, liquid water liquid Wolfram or liquid mercury?

 

eric

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[Miles Thatch]

From he Drive books archive

Nixe Tube Data > NixieGas.pdf

I was using the following excerpt from this book. Is it wrong or am I getting something mixed up?

[gregebert]

OK, that's once the tube is pressurized with the desired gas. However, to cleanse the tube of impurities, it must be baked-out and evacuated  to a rather high vacuum. Even at a high vacuum of 1 micron, there are still an extraordinary number of gas molecules present, on the order of 10^16 per liter. For home-made tubes I would actually want to re-evacuate the tube a second time, and refill, to get even more impurities removed.

[Nicholas Stock]

That is also the purpose of using a getter too right? Remove the majority of the gaseous impurities before back filling with neon/penning gas mixture?

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[gregebert]

From what I've researched, getters target oxygen, but I'm certain there are other rogue agents lurking out there to ruin your neon work.

[Miles Thatch]

Ok, that makes more sense. So in that case High Vacuum is required to evacuate then. 

What sort of pump would I need to be looking for to achieve that?

[gregebert]

I bought an A/C evacuation pump from Harbor Freight Tools that supposedly can get down to 35 microns; I dont have any equipment to measure anywhere near that low. It was a relatively inexpensive pump, around 80 USD. I think it's sufficient to do some experimenting. My plan is to do some heating/baking while the system is fully evacuated, then pressurize with enough argon (it's cheap and widely available) to get a glow. If I can sustain the glow for several minutes while heating the tube, I will pump it down a second time to hopefully get rid of any additional released contaminants, then refill. After I've made a few of these, I'll make a decision to continue spending time-and-money, or decide my experiment was enough to satisfy my curiosity and move onto something else. I'm definitely not going to build nixies. There are a few other things I want to make that require a vacuum and some glasswork, such as a radiometer.

To do quality work, you will need another pump, typically a diffusion pump, which will get you below 1 micron and will be rather costly. The mechanical pump must first be used to pump down as much as possible, before the diffusion pump is used.

[Miles Thatch]

>  supposedly can get down to 35 microns

Is there a particular technical reason to not use the torr unit of measurement when discussing vacuum? Just curious if it's just personal choice or if there's a technical principal at play.

> My plan is to do some heating/baking while the system is fully evacuated

I have seen Dalibor do this in one of his videos. 

I've also seen it in this one as well at 10:24:

https://www.youtube.com/watch?v=uHv1f4_tDv4

Also here, another nixie making gentleman: at 6:57

https://www.youtube.com/watch?v=MyhmEUw4OL0

> To do quality work, you will need another pump, typically a diffusion pump, which will get you below 1 micron 

I don't think I've yet seen any of the nixie makers talk about exactly the sort of hardware they use, Just glimpses in an occasional camera shot. 

Do you reckon it's what Dalibur and these other gents use?

[gregebert]

I'm not an expert on vacuum systems, but the units I see most-commonly for low vacuums (such as what you would see in a typical engine or vacuum cleaner) are inches or mm of mercury; higher vacuums are measured in microns. One Torr (1mm Hg) is 1000 microns. It's a tad silly, because you cannot physically measure 1 micron of Hg in a manometer, though at room temp the vapor pressure of mercury is quite low, around 2 microns. 

I'm guessing that nixie makers will use whatever high-vacuum equipment they can find and afford, and from the brief video shots the setups look like they use high-quality (expensive) equipment. Nothing looked cheap or kludgy.

You can even use atmospheric air at low pressure to get a gas discharge.

[Miles Thatch]

Just wanted to roll back around to this point you made.

I've watched a demonstration of a diffusion pump by Applied Science:
https://www.youtube.com/watch?v=SrNVLCHrJtY&ab_channel=AppliedScience

Another video mentioned a diffusion pump not being a good suit in application where avoiding contamination is key and Nixie making seems like the sort of case scenario where contamination would cause failure in the nixie. I could however be wrong. Would this make diffusion pumps unsuitable as a starting point? 

[liam bartosiewicz]

They’re a great deal of videos on YouTube showing people making high vacuum devices like vacuum tubes and X-ray tubes using normal dual-stage rotary vane pumps. Seems like a functional nixie could be made without a turbomolecular or diffusion pump, it just might not last as long.

On Nov 27, 2024, at 2:38 PM, Miles Thatch <milesan...@gmail.com> wrote:

Just wanted to roll back around to this point you made.

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[Miles Thatch]

Right, but I believe that would mean it would require higher voltage for the tube to reach breakdown potential and discharge, right? 

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[liam bartosiewicz]

I believe so, also due to the fact that most people will just use air, or maybe argon as the gas due to the difficulty in getting neon

On Nov 27, 2024, at 5:22 PM, Miles Thatch <milesan...@gmail.com> wrote:



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