Re: Triggered spark gaps for coils

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

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Tesla729-at-cs-dot-com>

Hi all, 

You know, since we're discussing triggered spark gaps, 
I have been thinking about the effect of placing some ob- 
ject between two electrodes charged w/ HV. Case-in- 
point, I've noticed that with my big Jacob's Ladder (which 
is powered by a 100 kV, 100 mA x-ray power supply trans- 
former), I have to turn the voltage up w/ my variac to a pre- 
determined level before the ladder starts firing. I can turn 
up the voltage to where it is just below the threshold where   
the ladder will start firing (~50 to 55 kV). However, if I stick some- 
thing into the gap at this point, it will act as a trigger and the 
Jacob's ladder will fire. And it doesn't really matter what I stick into 
the gap. I can hold a piece of metal (with an insulated hot- 
stick, of course) or I can stick the end of a dry stick into the 
gap's narrowest point and doing this will cause the Jacob's 
ladder to fire off. Also, I can turn the variac doen several 
notches, so that there's no way that it would fire off without 
an external trigger (~40 to 45 kV), but it will be triggered in- 
to firing when I stick the end of that dry wooden, stick into 
the gap. I'm  sure that I'm not the first one to notice this, but 
all of this talk of triggered SGs got me to noticing this effect. 
I suppose, inserting even a fairly good insulator (dry wood) 
in a gap between to HV electrodes still disturbs the E-field 
enough to cause the trigger effect. Of course, the insert ma- 
terial would probably burn up pretty quickly if this method of 
triggering was employed into a Tesla SG and it would really 
be little more than a crude RSG, employing a mechanical 
means of insering and removing a "trigger" between the SG 
electrodes several hundred times a second. No good for Tesla 
service ;^( but an interesting phenomenon, never-the-less. 

My $.02 
David Rieben