The ultimate pressure is one thing, but the most critical is the nature of contaminants. Due to the low conductance of the tubulation and the short cycle time on sealex machines used for production, the initial vacuum in receiving tubes is not very good before the getter is fired, but tubes are well pre-cleaned and baked to get rid of organic contaminants and moisture. Then the remaining N2 and O2 is captured by the getter.
>From RCAs excellent "Electron Tube Design", pp. 510: "While a pressure in finished tubes in the region of 10^-5 to 10^-7 mm Hg is expected, this degree of vacuum is attained in present receiving-type tubes only by the use of getters. The pressure range covered on sealex-processed tubes may be from 10 to 500 microns (1 x 10^-2 to 5 x 10^-1 mm Hg} as read on a Pirani gauge, but the actual pressure in the tube is, of course, much higher." In a nixie tube, evaporable Barium getters are not common, but Zirconium pill getters are very common. I would bet the requirements for evacuation are similar to in receiving tubes, but maybe more relaxed still for a few reasons. Firstly, residual Argon is less of a problem in Nixies as it is already present in the Penning mix, while receiving tubes are very sensitive to residual gas which causes grid current. Secondly, due to the glow discharge there is sputtering, which tends to chemically and physically trap contamination. I've made Neon tubes without cleaning the glass, without firing the electrodes, and without bombarding. If left running for a while, they will eventually clean up to pure red due to self-cleanup. On Saturday, November 23, 2024 at 6:49:13 PM UTC+1 Instrument Resources of America wrote: > I saw bombarding being done. I sit here now shaking and shuddering from > the experience. Here is a fairly detailed video of neon sign > manufacturing. https://www.youtube.com/watch?v=kH635AEawGY > The bombarding process starts at about 12:30. The demonstration that I saw, > they deliberately drew a two foot arc just for show. It was impressive, and > S-C-A-R-R-Y. This may not help you with your endeavors, but it is > interesting, and mentions 'neon' a number of times. > > Ira. > > > > On 11/22/2024 8:27 PM, gregebert wrote: > > > Several years ago I researched neon signage, and you need a high-vacuum, > around 1 micron (10-3 Torr). The books I have didn't get into specific > vacuum levels, as there are multiple ways to cleanse the tubes, notably via > bombarding. They did not cover nixie tubes. > > To get micron-level vacuum, you need a mechanical pump to get around 100 > microns, followed by a diffusion pump. There might be other ways to get the > required cleanliness without a diffusion pump, but I dont have any details. > If you just want to do some experimenting, start with a mechanical pump. I > plan to do that soon, as I have a small pump used for evacuating air > conditioning equipment. > > Some of the reasons I'm not doing neon work are the cost of the equipment, > the dangers of bombarding, need for mercury to extend tube life, and I > expect it to be difficult to find getter material. All I want to do is get > some sort of discharge glow, and play around with easy-to-find gases like > argon and helium. > > I saw a mention in the Weston book of pressures in the 10-2 to 10-4 Torr, > though it covers theory of operation rather than fabrication details. > On Friday, November 22, 2024 at 12:33:28 PM UTC-8 Miles Thatch wrote: > >> >> [image: vac.png] > > -- > 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 view this discussion, visit > https://groups.google.com/d/msgid/neonixie-l/7e19cde9-eb07-42fa-bb3b-2ccf0d4b22a6n%40googlegroups.com > > <https://groups.google.com/d/msgid/neonixie-l/7e19cde9-eb07-42fa-bb3b-2ccf0d4b22a6n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > -- 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 view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/9d4d1100-0621-4f3a-b112-31c6a7c29ff5n%40googlegroups.com.
