Triggered Spark Gap
The drawing above shows the lay out of my triggered
spark gap. The case is made from a 6" length of 5" OD X 2 3/4" ID
PVC bearing stock, capped on both ends with two 5" OD X 1/2" thick pieces
of polycarbonate sheet. The end caps are each held on with six 2"
long 3/8-16 nylon bolts. The main electrodes are 1 7/8" steel ball
knobs with 3/8-16 tapped holes supported on 3/8-16 threaded rods of 18-8
stainless steel. The trigger electrode is a piece of 1/8" OD tungsten
rod. All of the materials were purchased from McMaster-Carr.
In operation, the right hand electrode is grounded
and the gap is set wide enough so that the high potential on the left electrode
will not jump the gap. To fire the main gap, a high potential is
applied to the trigger electrode, causing an arc to form. The plasma
generated by the small arc increases the conductivity of the air between
the main electrodes, allowing the main gap to break down.
This picture shows the finished triggered gap,
with one end removed. The ground electrode can be seen through the
end plate and the trigger electrode is sticking out of the top of the PVC
case. The high potential electrode, mounted to the other end cap,
is seen on the right of the picture.