NST & Sparkgap

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

Original poster: "Michael Rhodes by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rhodes-at-fnrf.science.cmu.ac.th>

I have built a 4 gap static gap with tungsten electrodes mounted
in machined stainless steel heat sinks.  I connected my 15kV-at-30mA
NST to it (without cap and primary) to check the gap firing voltage.

 From my calculations using Paschen's law, breakdown in air at
STP would be 29.83kV at 1cm.  This equates to a total gap space
of 7.112mm (.28") based on 21.2kV peak voltage.  I set each gap
to 1/4 of this 1.78mm (.07").  The NST rated input voltage is 230VAC
connected to a variac.  If I turn the variac up the spark gap
begins firing continuously at 110VAC.  What do you suspect
is the reason for it to fire so early?.  I am in southeast Asia
and it is now hot (30 C) and humid.

I'm reluctant to increase the gaps but if I have to can I increase
just one gap to make up the difference?  Difficult to get to the
gaps now.  I suspect I am losing a lot of 'bang' due to this.

Oh, by the way - this was 'first light' for me today.  I will give further
details on my coil project later after the university science fair is
over and I have more statistics on the output.  It is not in tune yet
due to having to rush to assemble the parts in one day (parts where
constructed in 3 weeks) but it is already producing
30cm sparks and the students who assembled were surprisingly
excited by it all.  I will be assembling a web page for it also.

   -------------------------------
   Michael Rhodes
   Senior Researcher
   Fast Neutron Research Facility
   Chiang Mai University
   Thailand
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