Gas pressure in nixies...

[Nick]

What gas pressure is there in nixies? I suspect just a few Torr or approx 1 kPa?

And how much Hg was put in each tube - looking at Ar or Ar/He-filled display tubes which use up to 200mg of Hg (but can be a metre or more long), a pill of about 1 to 5 mg might be needed.

Dalibor - what do you find best? Thoughts?

Nick

[Jon]

I'd love to hear from Dalibor on this. Until then though... A quick surf through the literature gives values of 40mmHg (or torr) up to 125mmHg (acknowledged as high pressure).

Jon

[AlexTsekenis]

It is in the 50 mmHg ballpark for the IN-13 bargraph (white top).

Alex

[Dalibor]

Hello!

I use 30 torr pressure in my tubes, the gas is a mixture of 99.9% Ne + 0.1% Ar. Digits in my tubes are not so sharp as in original Z568M, I think they use 35-40 torr (higher pressure = thinner glow), I prefe a little bit more fuzzy look. The purpose of Ar here is to lower the striking voltage, anything from 0.01% to 1% will do the job.

Mercury - I think in z568m tubes will be 2-3mg of Hg, I use 4mg (I have bigger envelope). IMHO, the actual amount of mercury needed is based on surface of the inner system parts like digits, anode cage, micas and so.. The amount of mercury vapours present in relatively high pressure of 30 torr is negligible. From what I read, the amount of mercury is not critical. From my experiments, when I tried higher amounts (8mg), the glow had strong and ugly blue-white haze.

Regards!

Dalibor Farny 

Dne středa 14. ledna 2015 12:09:45 UTC+1 Nick napsal(a):

[Nick]

That's really useful information - thanks!

Do you "bombard" or otherwise cleanse the tube during evacuation prior to backfilling? Induction heating? I'm thinking of the nixies I want to refill - when the tubulation broke, air and general rubbish will have been sucked in and I'm not sure how to get rid of that.

With neon tubes, you use a process called bombardment that hugely overdrives the tube using upto 15,000 volts and maybe 300mA to cook the tube up to several 100 degrees C - this process also activates (converts) the special coating on the cathodes lowering the work function and making the tubes more reliable - you have the vacuum pumps running whilst this is going on and that sucks all the rubbish and moisture etc. that's been burnt off out of the tube prior to backfilling with whatever gas you're using (Ne, Ar, Xe etc.).

Nick

[Nick]

Just checked my copy of Weston, Cold Cathode Glow Discharge Tubes, (ILIFFE books, 1968)

In section 9.4.3, page 334, he's pretty clear - for long life and clarity of view, the Penning mixture should be 99% Ne and 1% Ar and the pressure should be about 30 Torr...

Nick

[Alek onet]

In polish nixies they used 33 Torr of mixture 99% Ne and 1% Ar.