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Vacuum spark gap efficiency

Original poster: "Laurence Davis by way of Terry Fritz <twftesla-at-qwest-dot-net>" <meknar-at-hotmail-dot-com>

hey all,
  are vacuum spark gaps comparable to an air blast gap?  I saw a gap that 
might have been either air blast or vacuum. so I copied it from memory.  
came up with a vsg with 3/4" copper end caps with 4 1/8" holes drilled in 
them.  I fired the coil up and it did quite well even without a vacuum, but 
even better with it. my other gaps are quite comical to look at. the VSG 
doesn't even get warm when running for 5 or 10mins. plus i put a welding 
plate over it so I can watch the gap ALL DAY long.

first, I made the contacts with four holes. reason: I wanted turbulent air 
flow around the contact surface to quench the gap more efficiently.  I 
looked at each hole in the contact as producing a wave front and thus nodes 
inbetween each gap.  I guessed that the nodes from each contact wouldn't 
line up and therefore would disturb the flow.  I have another set of 
contacts that I will just drill a single hole in each to prove my theory.

but the odd question.
okay since the vacuum is affecting how long the gap is or is not firing,
would it then be a conclusion that affecting air flow would affect dwell 
time (if I'm using the term right).  and if so, would you then be able to 
match the nst impedance to the tank capacitor by adjusting the vacuum. lower 
vacuum = more ions = less cap charge time. or am i confusing cap charge 
relating to resonance of the tank circuit. meaning that whether the cap is 
charged fully or 50%, it will change the resonance of the tank. (i'm 
thinking it won't and therefore charge doesn't play a role, such as the 
capacitance is more like a response-time for the charge to move thru the 

tnx for listening.
larry d.