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Re: small tube filling pressures
Morgan wrote:
>> in fact I have a 20 mm 4
>> foot tube that was fill by opening the new red gas bottle and letting as
much
>> in as will go (guessing around 3/4 atm); it runs hot and never stops
snaking.
>> It is little different in light output.
My physics too are less than keeping up w/ the tube pressure discussion,
but I'm curious about the snaking phenomenom.
--Why is it that such a high pressure of gas creates this effect? Some
tubes I've played w/ by putting in high gas pressure seem to just create a
well defined, fine line inside the tube.
--What is happening when snaking occurs in other units that are processed
in the "standard" fashion? And why, if it does occur, does it stop during
aging in?
***
According to Cobine's Gaseous Conductors (Dover, 1941), the mechanism for a
gas discharge tube is this. The ions created by longitudinal electron
collisions with the neutral gases are in equilibrium. The steady state
condition is achieved by these ions migrating radially to the walls of the
tube and discharging to a neutral atom on the wall. If the mean free path to
the wall is large, as in a large diameter tube, or with a dense gas, the ions
cannot reach the walls, and migrate outwards to a point where a steady state
is reached with the unionized atoms in the space between the ion column,
which conduct the ionic charge without ionization of the atoms, since they do
not have the kinetic energy to ionize them. These ions are therefore trapped
in the column, and the result is direct heating of the gas by metastable
de-exitation caused by collisions in the intervening space. This heat is
channeled into convection currents, or if intense enough, into turbulent
vortexes. This causes the snaking or pinwheels which we see.in a curing tube.
Jeff