[Prev][Next][Index][Thread]
Re: red 8 mm tube pressure
Frank; when you have a very small volume (6mm 2 foot long tube vs. 15mm 8
foot tube) it obviously only takes "a few" molecules to reach 10mm gas
pressure as compared "to the many" molecules it would take to reach that same
gas pressure in the larger voulme tube. All tubes have some gettering effect
in the electrodes (ageing in is the most obvious example); but this gettering
continues to go on for the life of the tube. Although it is worse for red
than blue gas, these molecules are becomming embeded in the electrode shell
(and maybe trapped through plating on the wall of the glass of the electrode
shell) - they are being removed, or better, removed from service of the tube.
As this continues to go on there comes a time when there are so few
molecules that the tube will not make light (or fail in a couple of very
specific ways). So, in order to increase the lifespan of small voulme tubes,
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