[Test-Equipment] Nixie project

[Mike Manes]

The E-field gradient in a gas discharge tube isn't nearly high enough, so
it does take an energetic event to kick an electron off most ionizable gasses.
But fortunately, there's plenty of cosmic radiation out there to make it
happen most of the time.  Having a bit of local excitation does help - and
for some gasses, even visible light has enough energy to free up an electron.
The added radiation sources do help overcome the light sensitivity effects
to stabilize the ignition voltage.

Once an electron is free, it gets accelerated by the ambient E field, and if
it has enough free path and E-field gradient to accelerate to sufficient
energy, it'll knock another electron free, and so on, culminating in a plasma
discharge.  A partial vacuum in the gas provides that essential free path.
The typical fluorescent lamp is pulled down to about 2 or 3 Torr absolute,
e.g.

73 de Mike W5VSI

On 7/3/2010 01:25, hwhall at compuserve.com wrote:
> IF the nixies require some ionizing radiation to help them fire, IR or visible light will probably not help. Those are a non-ionizing radations (not to be confused with radioactive radiations). Ne lamps can be sensitive to light, however, and other effects as well but I've not researched the reasons. However, Ne gas should be able to fire (ionize) with sufficient applied voltage alone. I suspect the improved nixie performance noted by the original poster is similar to observations about very-old-stock filament tubes that improve when put in use. The nixies I run in my HB freq counter do get warm over time; maybe that is sufficient to cause a getter action?
>
> When I was playing with He-Ne gas laser construction long ago no one ever hinted that any radioactives had to be inserted in the construction to make them work, so I wonder sometimes about the origins of the info that gas discharge tubes in general must have some form of radioactives to make them work. Perhaps some gases do (i.e., hard to ionize), or some manufacturing methods used that technique to achieve a particular performance effect?
>
> Wayne
> WB4OGM
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> -----Original Message-----
> From: John Kolb<jlkolb at jlkolb.cts.com>
> To: Discussion of Electronic Test Equipment<test-equipment at mailman.qth.net>
> Sent: Sat, Jul 3, 2010 12:46 am
> Subject: Re: [Test-Equipment] Nixie project
>
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>
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> I wonder if an IR LED shining on them would be enough to allow them
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> to function-
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> it would be invisible to humans.
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> John
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>
> At 07:45 AM 7/2/2010, you wrote:
>
>> I have been working on a Nixie clock and when I first plugged in the 6 old
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>> nixies that I had only two of them would work.  I have had the clock running
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>> for a few days and now 5 out of the 6 nixies are working.  I remember
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>> reading somewhere that they need "radiation ionization" to operate and
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>> wonder if this comes from normal background radiation.  These tubes have
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>> been in the junk box for years.
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>> 73,
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>>
>
>> Bill, WA2dvu
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-- 
Mike Manes    mrmanes at gmail.com     Tel: 303-979-4899
"Things should be made as simple as possible, but not more so."
A. Einstein