Marx spark gaps (fwd)

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Original poster: <sroys@xxxxxxxxxxxxxxxxx>



---------- Forwarded message ----------
Date: Tue, 31 May 2005 17:57:40 +0200
From: Herwig Roscher <herwig.roscher@xxxxxx>
To: hvlist@xxxxxxxxxx
Subject: Marx spark gaps

Hello!

Trying to understand the function of Marx generators, I searched the 
web and found several descriptions like this:     

"The charging voltage is applied to the system. The stage capacitors 
charge through the charging resistors (Rc). When fully charged, 
either the lowest gap is allowed to breakdown from overvoltage or it 
is triggered by an external source (if the gap spacing is set greater 
than the charging voltage breakdown spacing). This effectively puts 
the bottom two capacitors in series, overvoltaging the next gap up, 
which then puts the bottom three capacitors in series, which 
overvoltages the next gap, and so forth. This process is referred to 
as "erecting".      

For a charging voltage of e.g. 20 kV the first gap should break down 
at 20 kV, the second gap at 40 kV, the third gap at 60 kV and so on. 
Consequently the gap distance of the first gap should be about .27", 
that of the second gap about .54", that of the third gap about .81" 
and so on.  

To my surprise I found, that all of the described Marx generators 
were said to have EQUAL gap distances (with the exception of the 
first gap, which is set a little bit closer sometimes).     

Looking for the reason of this unexpected recommendation I found:

"The Firing Probability of Coupling Spark Gaps of the Multiplying 
Circuit according to Marx" by A. Rodewald, Basel

This technical documentation contains a lot of useful information and 
could be downloaded from      

http://www.haefely.com/literature/pdf/scientific/e1-04.pdf

I am hoping that you will find it interesting as well.





Bye		Herwig

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Greed is the root of all evil !
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