Re: [TCML] Rectifying a Tesla coil

[Sfxneon@xxxxxxx]

Hi David, all,
 
Yes, a fluorescent tube would withstand even the deepest vacuum obtainable. 
 
Look at it this way, the absolute pressure difference that can exist  between 
the inside of a vacuum tube and the atmospheric pressure  outside is no more 
than about 14.7 pounds per square inch, and even less  above sea level.  
 
Normally, a fluorescent tube is backfilled to about 2 to 3 Torr of argon  (or 
other noble gas mix + Hg). Standard atmospheric pressure at sea  level = 
about 760 Torr, (which = about 14.7 PSI, or about 30" of  mercury column) so, the 
pressure differential of a standard fluorescent tube is  only about .05 PSI 
less than one with a hard vacuum. 
 
It's a bit deceiving to think that the higher the degree of vacuum,  the 
greater the implosion force that would exist (since that is true with  pressure 
and ex-plosion forces), but that's not really so with a vacuum. It  can't be any 
greater than the pressure outside the tube. Once you reach  the single digit 
Torr range, there's not much real pressure difference  below that, so a tube 
that will withstand a rough vacuum will most likely  withstand an ultra-high 
vacuum too. 
 
It's really amazing how that 14.7 PSI adds up over a surface area, though.  
If I did the math right, a 4 foot tube would have over 200 square inches of  
surface area, and at 14.7 PSI outside, the total force distributed over the  
whole tube would exceed 3000 pounds! It's no wonder those things implode  with 
such a BANG!
 
Tony Greer
**************

In a message dated 8/31/2008 10:33:33 P.M. Central Daylight Time,  
drieben@xxxxxxxxxxx writes:

Hi Tony, Ben, all,

I was also wondering if the ultra-thin walls  of a glass flourescent
tube could withstand the pressure gradient of a high  vacuum with-
out sustaining collapse (imploding)? Even if it could, it would  still
prove extremely fragile!

David
 



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