[Prev][Next][Index][Thread]

Re: stepped leaders

Tesla List wrote:
> 
> >From leyh-at-ix-dot-netcom-dot-comFri Aug 23 21:49:11 1996
> Date: Thu, 22 Aug 1996 22:59:59 +0000
> From: "G.E. Leyh" <leyh-at-ix-dot-netcom-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: 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?
> 
> -GL

Gerg,

Good post!

No we haven't done this, yet.  We will soon!

I has noted, from prior experiments, that the ions remain around for some 
minutes after a coil is turned off.  Most of them are gone in seconds 
after shutdown.  The heavy Tesla coil arcs, inorder to grow, however 
require vast numbers of highly excited ions in the immediate vicinity of 
the previous arc channel.  The bulk of these ions recombine in under 
100ms.

I have recently done a number of quantitative studies with a Keithley 610 
 and a Cary vibrating reed electrometer and have noted that ion lifetimes 
are much longer that we would like to think.  The highly ionized gas 
atoms move very rapidly out of the arc channel area due to kinetic energy 
obtained in the channel.  The kenetic energy is provided by: 1. Air 
currents (the weakest KE provider). 2. Thermal channel heating (second 
most powerful KE provider) and 3. Coulombic forces (most powerful KE 
source)  These ions can diffuse out over vast areas 100 feet or more away 
and still charge isolated capacities minutes after coil shutdown.

Following shut down, only the air currents move the ions.  We are still 
intently studying a number of related phenomena.

Richard Hull, TCBOR