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Re: A&E Tesla coil, and Mind Freak. (fwd)

Original poster: "Peter Terren" <pterren@xxxxxxxxxxxx>
You can still deliver high voltage pulses to your testbed. The voltage is not changed. Spark growth occurs as each streamer grows on the previous one in the electrical field between the toroid and earth. There is a chaotic nature due to a variety of factors one of which may be cosmic radiation (look at a working cloud chamber to understand why). The repeated hits at 100kHz seem to be close enough together to result in spark growth with streamers. My impression is that higher frequencies are not as effective (energy lost as EM radiation or capacitatively) nor at low frequencies or DC (only one hit or too far apart for much ionisation to remain). I have pictures of streamer growth using streak photography to enable features of about 5us to be easily seen. The technique is here: 
http://tesladownunder.com/HighVoltage.htm#High%20speed%20Tesla%20spark%20photography
A typical photo of a streamer has the uppermost channel developing first then 5us later the next lowest one appears etc until it reaches the earthed object and a full ground strike occurs which is the lowermost bright channel which is about 50us after the first. 
http://tesladownunder.com/HVRotMirrorStreamerHit1.jpg
Terry Fritz also did a lot of work on this stuff with a typical picture here. As he is in the northern hemisphere the time sequence is from bottom up. 
http://drsstc.com/~streakcam/instruments/SET-14/strike.JPG
A lot of these details are discussed in the 4HV forum thread.
http://4hv.org/e107_plugins/forum/forum_viewtopic.php?15766.0

Not sure if that helps
Peter


Original poster: Tom Perigrin <tip@xxxxxxxxxxxxxx>
At 01:15 AM 12/22/2006, you wrote:

From: Peter Terren <pterren@xxxxxxxxxxxx>
Many people have assumed that spark length of DC sparks extrapolates to RF
sparks from a TC. Not so. Spark length in a TC grows due to repeated hits
far longer (eg 3 or more times) than expected.  This is easily proven by
doing single shot sparks which are ridiculously small even with huge coils.
I have been interested in using a single shot or pulsed Tesla Coil to deliver high voltage pulses to a test bed. Now, upon reading this, it seems that this won't work as well as I had envisaged. Yet I am a bit confused... Peter says that the spark grows longer due to repeated hits. Does that mean that it:
A) "walks out" by first hitting close to the coil, and this ionizes a bit of air further out which allows the next discharge to go to a more distant ground, and this process repeats until some function of resistance of the ionized air path versus voltage and power dictates that it can't extend any more? If not... then I don't see how multiple discharges would increase the distance if the first discharge has to make the full distance... because discharge(1) won't know that discharge(2) through discharge(n) are following.
B) there is actually some electrical characteristic of the coil that increases it's efficiency/power/charge/? as it cycles several times?
C) the actual difference is not distance, but power of the discharge, as the first discharge serves to slightly ionize the air and each subsequent discharge finds a less resistive path, thus allowing more power to flow.
In the first scenario... the "walking out" scenario... would a preionization of the desired air path suffice to allow for a good discharge along the desired path? In fact, would such a preionization be almost neccesary to overcome the semi-random fickleness of the discharge to follow a desired path? 

Thanks for your help