Re: stepped leaders

Hi All,

A high-speed camera is actually not required to see the streamer
building upon itself, if the speed of the rotary gap is slowed 
down considerably.
At gap break rates in the range of 30 to 80 pulses per second (pps)
the streamers wander around quite slowly, and emerging streamers
often take a good fraction of a second to grow to full length.
The streamer growth at this gap speed is actually noticable with
the naked eye.  
A frame-by-frame analysis of 8mm video from a recent coil session 
shows quite clearly that the streamers never reach their full 
length in a single gap firing -- a typical streamer starts out about
2 to 3 feet long and grows around 18 inches in each successive
video frame (NTSC - 30 frames per sec).
At gap speeds over 100 pps it starts to become hard to see the 
streamer growing with the naked eye.
At gap speeds under 30 pps the streamers have a hard time growing
much beyond their initial length. This is not surprising though,
as most of the ions from the previous streamer path 33 msec ago
have either diffused or re-combined.  For those who are interested
there's some nifty charts of ion lifetimes in electric arcs on 
pp 359-360 in 'Gaseous Conductors' (Cobine, 1958).

Has anyone else experimented with their coil at slow gap speeds?