Re: DC secondary components

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

>
> > One approach might be to run the secondary current through an
> > electrolytic cell and measure the amount of metal added or removed
>
> A cunning solution!
>
> Or perhaps a minute deflection of a compass needle close to the
> secondary.  Anyone got an aurora detector?
Using the compass needle as a mechanical low pass filter... I think you'd
need integration times much much longer to get the measurement up where it
could be feasible...  A magnetized needle on a quartz fiber and magnetic
damping, perhaps with an optical pickoff (how 30's vintage...).. Very low
loss in the suspension.  I think you'd have problems with stray fields
corrupting your measurement.  The field from the wire would be pretty darn
low, and your sensor would have to be in a shielded can (electrostatic
forces would pull that needle around all over the place).

For those folks looking for a good science fair project, this has all the
elements of classical applied physics research problem.  Some theory to
research, some really mind bendingly clever apparatus to design and
construct, lots of measurements and quantification of error sources, and so
forth.  The craftsmanship required would be of a very high level.

>
> [Applying a DC pedestal to the coil base]
> Jim wrote:
> > an intriguing idea.  Especially if you were to make the voltage a
> > significant fraction of the topload voltage during breakout,
>
> I was wondering if it might help preserve the remnants of streamer
> channels between bangs, thus enhancing subsequent growth.
>
> > You'd want a good RF bypass cap across the power supply
>
> A non-trivial component, I imagine.
No.. I think a good transmitter grade cap would work.  Say at 100 kHz, you'd
want the impedance of a few ohms, so the voltage didn't rise too high.  C =
1/(6.28E5*X)... Ball park it at around 0.1 uF...  A few of the geek group
caps might be a good way to go.. although, you might want a series parallel
string (series to get the voltage up, parallel to reduce the series
impedance).  What's the ESR of the geek group cap at 100 kHz (probably a
more important value for this application)

The resonance would shift up very slightly, since you'd have something like
100 pF in series with 0.1 uF... resulting in slightly less overall
capacitance.

>
> > You'd want a small TC (low voltage) for this so you could really
> > make a difference. A few kV out of 500 kV on a big coil might not
> > make a difference.  10-20 kV out of 75-100 kV though...
>
> Hope someone rises to the challenge, to see what a DC supported
> breakout looks like.


Again, this would make an excellent science fair project... Much better than
the usual "build a TC" project.  Interestingly, the Greater San Diego
Science and Engineering Fair (GSDSEF), which is a pretty big and prestigious
one,  just sent out a list of "projects we do NOT want to see, because they
have been done to death, or have little value", and among the usual "effect
of music on plant growth", etc. projects was the "build a tesla coil"
(unless you do something special with it..)