[setori88]

That induction heating step is critical. Ensure you heat metal whilst the vacuum system is still pumping otherwise if you heat the metal after the tube is sealed the metal will out gas giving you bad vacuum, completely destroying your Nixie tube. It's a pleasure to see such refined work, many many frustrating mistakes were made to reach this level of refinement.

[rzzzt]

Isn't that why the getter is added?

[grkvlt]

What is a 'getter' though? And what does it actually do?

EDIT - Wikipedia [1] says it's a strip of (barium?) metal that is evaporated to react with any remaining gas/moisture particles in the tube and deposit them on the surface safely. It causes the shiny metallic film seen at the top of some tubes, I think?

[1] https://en.wikipedia.org/wiki/Getter

[rzzzt]

You are right, another article touches on this topic: https://en.wikipedia.org/wiki/Vacuum_tube#Vacuum

[setori88]

That getter is fascinating, it's a new concept to me. Recently we blew a picoammeter because we fired up a vacuum guage in UHV after disconnection from the roughing pump. The vacuum guage out gassed massively giving us shit vacuum, this then fried the picoammeter and left us scratching our heads for a few hours. Firing the vacuum guage while still connected to the roughing pump would have solved this problem. Thanks for sharing the getter information.

[dekhn]

A month ago, nothing you said would have made any sense to me, but after trying to make a glow discharge tube, it is eminently obvious (you have to be extremely careful with sensitive vacuum gauges).