As I understand it, for current to flow in a "cold-cathode" tube, the gas atoms must impact the cathode to pick up electrons, and the attraction due to the potential difference means they hit it fairly hard. So the only reason the cathodes are called "cold" is that they are not significantly directly heated by I^2R of current flowing along them, nor indirectly by infrared radiation from a heater filament. Despite the lack of those heating mechanisms, "cold" cathodes actually get quite hot. In some nixies, when looking from the side you can see cathodes distort slightly from thermal expansion.
On Monday, June 22, 2015 at 12:40:45 PM UTC-7, gregebert wrote: > > Perhaps there is a thermal component hiding in the underlying physics of > tube wearout, such as exp(aKT), where K is Boltzmann's constant, and T is > absolute temperature. Tubes will run hotter at higher current. Until now it > never even occurred to me the cathode surface temperature of a nixie could > be significantly higher than the glass envelope. > > I'm not sure how the heat generated by a nixie tube is produced, and more > importantly, *where* it's produced. The cathode itself isn't actually > glowing; it's the ionized gas surrounding the cathode that produces the > glow. Most likely the ionized gas is the hottest part of the tube, but it's > close proximity to the cathode will cause it to heat. > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/685c90f4-5bb0-4e29-befc-5f04dd00c0b1%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
