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Re: red 8 mm tube pressure
you need to go up in pressure.
An example is the gas pressures that the automobile brake light people are
messing around with to get decent lifespan out of those tiny tubes: 50 to
100mm.
Morgan
Actually, Morgan, that's a separate issue entirely. The reason the auto brake
lights are at a higher pressure is the same reason that flashlamps, for
example, short arc flashlamps and arc lamps have pressures up to 20
Atmospheres of Xenon, because in discharge lamps there is a principle that
they scale with E/xp=const,
where x is the discharge length p the pressure and E the electric discharge
potential. This is called Paschen's Law. It of course only applies to the
first order in the simplest models but is a good rule of thumb, sort of
"ideal behavior". When the arc length goes up, the pressure must come down in
order to sustain the same discharge at the same voltage, because there are
more atoms (not molecules in our case, we hope, molecules are very resistive)
for the electrons and opposing ions to collide with along the path which
raises the resistance of the arc. If you shorten the arc to only a few
millimeters, you must raise the pressure in order to get the same light
output that you would expect to get in the longer arcs using the same
available voltage. This is called scaling the lamp design.
Hope this helps.
Jeff Golin