Re: Spark Gap Distances for Marx Generator

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mike Harrison by way of Terry Fritz <teslalist-at-qwest-dot-net>" <mike-at-whitewing.co.uk>

On Mon, 05 May 2003 07:04:33 -0600, you wrote:

 >Original poster: "Mccauley, Daniel H by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>
 >
 >
 >Regarding spark gap distances for a marx generator, I am seeing two schools
 >of thought.  One school seems to make all
 >spark gaps the same identical distance while another seems to make the
 >primary gap closer together than the other gaps.
 >I so far have opted to space all my gaps identically.  With the 1Meg
 >charging resistors between each capacitor, I figure there will be enough
 >voltage drop up the chain on each one to prevent another gap other than
 >primary spark gap to fire first.
 >
 >What are your experiences and thoughts?
 >
 >The Captain
Partly depends whether you are using forced triggering, or relying on 
overvoltage berakdown of the
gaps.

In the former case, you need to be sure they don't break down  at Vin, but 
reliably fire at Vin*2.

The latter case is much more tricky and usually requires some tweaking.
You want to make sure all the caps are charged before it fires, so making 
the last gap smaller would
seem to make sense, as it will fire when the caps at the end of the chain 
have charged,  but things
don't always work out like that...! I think one issue is that when the 
first gap fires, the next
needs some capacitive loading to ensure enough enough overvoltage, 
so  making the last gap smaller
may only work if there is also some topload capacitance.

Things get a LOT easier with forced triggering, either with a HV relay or 
some mechanical means to
reduce the gap distance.