[Test-Equipment] Nixie project

[J. Forster]

Not quite. Breakdown happens when the electric field exceeds a critical
level. The electric field needs to be high enough so than when a collision
ocurrs, an avalance happens. Sort of like a chain reaction.

http://en.wikipedia.org/wiki/Townsend_discharge

The terminal voltage for breakdown is the integral of the electric field
between the electrodes, so if you have a wider electrode spacing, the
breakdown voltage is higher. The pre-ionization sort of fills the tube
with a few ions so the electric field is more uniform and breakdown is
more predictable.

The pre-ionization sort of smooths out the electric field in the area
between the electrodes. The electric field still has to exceed the field
needed for avalance everywhere along the entire path length.

FWIW,

-John

=============


>> The radioactive pre-ionization is to improve triggering stability.
>
> So if I understand this right, it lets the tube go into conduction
without
> having the applied voltage first rise to the firing voltage, which is
normally a good deal higher than the voltage to maintain operation.
Does
> away with a voltage spike, so to speak, in regulator type tubes.
>
> Wayne
> WB4OGM
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