Lucky,as Dieter pointed out, the blue- or purple-ish haze comes from other gases or substances in your Nixie tube. Neon glows red / orange, depending on pressure and voltage. The little Argon in there makes it almost completely orange / yellow.
But there are other substances in the tube, like mercury, that is used to prolong the cathodes' lives. Mercury has a strong ultra-violet component, but also some visible parts in blue / green. (This is why you can only get red or blue/greenish genuine "Neon" tubes, almost all other colors are created using some fluorescence effect).
When you inverse polarity, nothing actually happens, except that the electric field changes its direction inside the tube. This, however, results in the electrons leaving the anode mesh and then moving towards the cathode. Electrons are not heavy, and so they are able to excite a gas atom to glow after a "flight" of only a few mm. They need a kinetic energy of something in the order of eV, and with 150V accelerating them (thus an electric field of 150V / cm) 1mm is enough.
OK, why is this important? In most Nixie tubes so-called getter materials are used. These are usually barium based chemicals who adsorb non-inert gas molecules (residuals of oxygen, nitrogen, or other impurities). These getters are usually mounted on the anode, because during normal operation, there are practically no electrons there, only the positive gas ions.
When driving the Nixie tube inversed, the electrons can excite the getter material. This has a whole other spectrum than the gas, so it creates all kind of funny lights. That is not good for the tube, though, because you might sputter the getter material with that, just like with the cathodes in normal drive. And in that case, mercury might not even help preventing it (I don't know for sure).
Hope that makes sense :-) Jens
IMO, Ucc is a rather odd term. That’s what triggered my first reply. Suppose we started to use ‘Siemens’ again. Or express capacitance in square meters. I had an old teacher once, who named every power supply with PSA. That stood for “Plaat Spannings Apparaat”, which is dutch for Plate Voltage Apparatus. As if the power supply was only suitable to power tubes with anodes and plates. Cheers, Frank *From:* JohnK <mailto:[email protected]> *Sent:* Friday, February 17, 2012 4:06 AM *To:* [email protected] <mailto:[email protected]> *Subject:* Re: [neonixie-l] Question on haze around nixie digitUcc is a common term for supply voltage [Google it]. The 'cc' is probably questionable in this case, but the U is common in Europe. Semi-related Factoid:- If you read early US books on wireless you will find the term "anode" used in a sentence when they mean the supply voltage for the tubes. Makes for strange reading today. eg, "..remove the anode if the temperature exceeds..." Maybe my post is one Lucky is having a crap-attack about. Well, I actually asked the colour of the haze so I could repeat answers given over the years ! Jimi always got a mention if it was purple. And as for 'invention' - you will never hear the end of that one. And because you thought it was finished with I am not allowed to comment - oh deary me.jk ----- Original Message ----- *From:* Frank Bemelman <mailto:[email protected]> *To:* [email protected] <mailto:[email protected]> *Sent:* Friday, February 17, 2012 1:10 AM *Subject:* Re: [neonixie-l] Question on haze around nixie digit So, is “invention” now a forbidden word? Sheesh... Yes I read everything. Dieter is NOT very helpful if he invents ‘new’ names for things. I can not recall someone using the “Ucc” ever being used in this and previous Neonixie newsgroup. I am sorry you posted too. But hey, it happens. Learn to smile Knipogende emoticon *From:* Lucky <mailto:[email protected]> *Sent:* Thursday, February 16, 2012 3:31 PM *To:* [email protected] <mailto:[email protected]> *Subject:* Re: [neonixie-l] Question on haze around nixie digit Don't know who is worse here. Dieter for first stating 'Ucc' (I think maybe we are talking Vcc?) Regardless Ucc had been taken to mean something "cold cathode voltage" Have you not bothered to read the entire thread? Me for repeating the same (or maybe just being naive) Or 3 useless replies 2 of which are sarcastic, and one mocking the 'Invention' word which I thought we had finished with! Do you not wish to help anyone out? Do you not have anything to add, informational or knowledgeable wise? If not why answer? Just to mock? And I notice you did not jump all over Deiter when he said "Second, the lower the Ucc (cold cathode voltage) the higher the haze" Talk about childish! Sorry I posted. Post --You received this message because you are subscribed to the Google Groups "neonixie-l" group.To post to this group, send an email to [email protected].To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.--You received this message because you are subscribed to the Google Groups "neonixie-l" group.To post to this group, send an email to [email protected].To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
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