Re: [TCML] Large Plasma Tube

[Ed Phillips <evp@xxxxxxxxxxx>]

The main problem is a large globe pumped to a very high vacuum.  When 
these implode lots of flying glass everywhere.

With normal museum display type plasma globes, they are only pumped to 
5,500 microns (7600 is atmospheric) and then back filled with neon, 
xenon, argon, CO2, and other gasses so the mixture is usually around 
6500 microns.  An implosion at these pressures are no where as severe as 
a high vac implosion. With higher vac you should always wear a face 
shield and be sure your globe was designed to handle the pressure at 
which you intend to operate it.

Many experimenters buy the cheapest globe possible, pump it to a very 
high vac, and have no vac pressure monitoring gauges so they really have 
no idea where they are on the micron scale.  Doing this is usually a 
receipe for disaster.  Do the engineering properly prior to the 
experiment or don't do the experiment!  Always be safe --- FIRST!

Dr. Resonance"

   With devices like this the only reason for reall low pressure is for 
outgassing and decontamination.  As far as pressure goes, the stress on 
the bulb isn't much greater at 1 micron than it is at a quarter 
atmosphere.  A hardware cloth shield around the vacuum chamber is a 
pretty good safety measure.

Ed

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