Re: 1pF+220k....

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 02:59 PM 7/2/2005, Tesla list wrote:
> Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>
>
> Hi All,
>
> I now think our long time streamer load estimation of 1pF/foot + 220k ohms 
> (series) for a streamer load we use in models should have the "1pF/foot" 
> part replaced by:
>
> The capacitance in pF is:
>
> C = 0.0666667 x L        from 0 to 30 inchs
>
> C = 0.15 x L - 0.25     from 30 to ? inches
>
> L is in inches.
>
> It really does not change many things much, but there is a lot of hard 
> evidence to support that this is a "better" estimation that agrees with HV 
> leader folks, models, and testing...


Hmmm..  While this empirically might work "better", I'm wondering what the 
physical basis is.

Longer sparks will, in general, be created by a higher power source, which 
will have a larger Topload C, which will have higher currents, which will 
make a larger diamter spark channel, but I doubt that channel diameter has 
enough effect on C.

More "furry offshoots" on longer streamers?


Here's an experimental idea that might prove useful:

1) Take a given coil, and figure out a way to measure the C of the streamer 
(change in fres?) at sea level.

2) Take the same coil, run it in a low pressure environment (i.e. at 
10000-15000 ft MSL (Drive to the top of Pike's Peak, or some high mountain 
resort), where the breakdown voltage is lower, and hence, with the same 
power input it should make longer sparks.  measure the C of the streamers.





> Cheers,
>
>         Terry