Does the gas make any difference? What about heavier gases like Kr, Kr+I, or Xe?
https://www.youtube.com/watch?v=l3M0cY29Pq0
-Dan
On Sat, 18 Jul 2020, Kevin A. wrote:
I found an IEEE article which contains an anecdote from a Burroughs
engineer who worked on nixie R&D.
Link:
https://spectrum.ieee.org/tech-history/dawn-of-electronics/the-nixie-tube-story-the-neon-display-tech-that-engineers-cant-quit
To quote that article:
"Roger Wolfe, a Burroughs engineer, recalled the team???s first fragile
attempt: ???We put the tube on life test overnight. When we came in the next
day, so much cathode material had sputtered onto the dome of the tube that
the numerals were no longer visible. We had invented a tube with a 24-hour
life!???
After some tinkering, Wolfe wrote, they discovered that the addition of
mercury vapor would greatly extend the tube???s life span. The sputtering had
been caused by the accelerated neon ions striking the cathode. But when the
neon ions collided with the heavier mercury molecules, their energy dropped
below the point where they could damage the cathode.
???We secured a tiny ampule with mercury sealed inside, wrapped a few turns
of resistance wire around the ampule, [and] connected the ends of the wire
to two of the [tube???s] pins,??? Wolfe wrote. The tube was then sealed, and
the team ran current through the wire, which heated and broke the ampule,
releasing the mercury."
On Sat, Jul 18, 2020, 2:15 PM Jeff Walton <jwalton...@gmail.com> wrote:
Thanks for the information, Dalibor. Appreciate the findings with actual
supporting evidence. It would be nice to know the actual role of the
mercury in the process and how it protects the cathodes. Can you tell the
gas mixture in a tube with a spectrograph while the nixie is operating or
does that only show which gasses are ionizing?
I had a 6 digit clock with NL-6844A top view nixies which ran continuously
and didn't last a year before the digits became unreadable and couldn't be
healed. I believe that these are a non-mercury style nixie tube, but I
didn't know that when I bought them. I replaced them with slightly larger
NL-6091 tubes that have been running fine ever since (>4 years) with no
degradation or modification to the clock.
While my experience with this clock and these tubes is not scientific,
I've certainly come away with a belief that whatever role the mercury
plays, it seems to be essential to long life and cathode protection. Not
sure why anyone would want to make a tube without mercury or other element
that helps protect the cathodes and provides long life.
Jeff
-----Original Message-----
From: neonixie-l@googlegroups.com [mailto:neonixie-l@googlegroups.com] On
Behalf Of Dalibor
Sent: Saturday, July 18, 2020 6:54 AM
To: neonixie-l
Subject: [neonixie-l] Mercury not all it???s cracked up to be?
Hi!
Paul - could you please share the source of that information? I would like
to look at it.
My experience is that Hg is absolutely necessary in nixie tubes.
Few tests I made:
1. two tubes - one with, one without Hg. Both running at 5 times rated
current on cathode 8. After few weeks, Hg free tube sputtered so much metal
that it caused internal short between 8 and anode, test ended. The Hg free
tube was heavily poisoned on unused digits, they were all practically
black. The 8 had 50% metal sputtered away.
The Hg doped tube was visually just like a new tube, no black deposit, the
8 was slightly more matte than other digits. Light poisoning on unused
digits, quick healing reverted it all back to 100% condition.
2. Comparison of poisoning development between Hg and Hg free tubes. Two
clocks, 6 tubes with and 6 tubes without Hg, no anti-poisoning routine,
rated current. I wanted to see whether the Hg only slows down poisoning
development or it has also other impact on the tubes. After 12 months, the
Hg free tubes were all black inside, even tubes (2,4,6) had no poisoning on
cathodes, 3,5th tubes had heavy poisoning on 6-9, other digits ok. 1st tube
had cathodes 0,1,2 thinner, 1 being half eaten away. Other digits heavily
poisoned.
The Hg doped tubes had poisoned 1st tube (3-9 digits), odd tubes had
slight poisoning on 6,8,9.
What is interesting - the poisoning patterns (location of the poisoned
segments) were different between Hg free and Hg tubes - this suggests some
other differences happening inside - I???ve set up more tests that are being
run right now.
My conclusion is that a Hg free tubes are difficult to keep without
poisoning and also recovery from poisoning at rated current is usually not
possible.
I have photos and more tests - will post next week..
Regards!
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