Re: arc length/secondary length and magnifier questions

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

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Jimmy and all,

It ultimately comes down to E-field control - the secret is to suppress
initial breakout in regions where it's not desired, and promote breakout
(after holding off as long as possible) only in areas where you want it
to occur. This approach forces initial breakout to occur only in
directions that are initially "away" from sensitive areas such as the
secondary or the primary/strikering. 

A toroid performs this field shaping function better than most other
topload shapes. A toroid tends to "throw" sparks away from the secondary
and primary and reduces e-field stresses in the "shielded" region
beneath it. In these shielded regions, e-field stresses is kept below
the point where initial air breakout will occur (~26 kV/cm). The e-field
is permitted to rise significantly above this threshold in other (more
desirable) regions of the toroid surface. And, once breakout occurs, the
ultimate length of the air streamers can be MUCH longer than the output
voltage of the coil would otherwise suggest. 

By suppressing initial streamer formation in undesired directions, it's
possible to support leaders that are many times the length of the
secondary winding in a classical 2-coil system. By using multiple field
shaping toroids and other (less obvious) field control techniques in the
11E Magnifier, Richard Hull and the TCBOR were able to achieve sparks
that were fully 11 times the length of his 1 foot long tertiary
resonator! A shot of a 10 foot streamer hitting the camera(!) can be
seen in the bottom picture at this location on Richard's site:
http://www.richmond.infi-dot-net/~rhull/highenergy004.htm 

An excellent shot of the mapped E-field stress (as computed by E-Tesla
Version 6) for a classical 2-coil system topped with a toroid can be
seen on Terry's site:
http://hot-streamer-dot-com/TeslaCoils/BLTRstress.jpg

The reduced e-field ("shielding" action) underneath the toroid is easy
to see. Also, note the reddish e-field peaks at the toroid's upper/outer
surface - this region will be the area of initial breakout, thereby
directing streamers "away" from the primary and secondary. Any spark
launched from this region would need to take a much longer, looping path
in order to reach the primary. Using a toroid, it's relatively simple to
obtain streamers that are 2X the winding length for a 2-coil system.
With careful attention to e-field control (often using multiple toroids
for improved field grading) almost 4X has been achieved.

Best regards,

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
"Electromagically" (TM) Shrunken Coins!
http://www.teslamania-dot-com

Tesla list wrote:
> 
> Original poster: "jimmy hynes by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<chunkyboy86-at-yahoo-dot-com>
> 
> how can a tesla coil make an arc that is longer than the distance between the
> toroid and strike rail? i read that the coil nemesis could make 14 foot arcs
> with a 48" tall secondary. i also saw that richard hulls magnifier could make
> 10 foot arcs when the extra coil is only 3"x12". i realize in the
magnifier the
> extra coil doesnt see all the voltage. if, as i've read, the overall coupling
> is the same then it should see most of the voltage, so how can the extra coil
> be so small and make such big arcs? what keeps the arc from taking the
shorter
> path to the strike rail? what limits how big of arcs you could get from a
given
> resonator? is it break down of the resonator or does it start arcing to the
> strike rail?
> 
> JImmy
>