Re: [TCML] (somewhat) high speed plasma photos from coil/capacitor interactions

[Josh Bailey <josh@xxxxxxxxxxxx>]

Thanks! Yes, mostly we are just exploring here - for me here the major 
"advance" was being able to reproducibly/reliably photograph this end 
stage. I can get a pretty decent image of at least one "plasmoid" 4/5 
times now with my light trigger setup.

It'd be great to be able to image the entire progression; this will 
require of course different triggering techniques, exposure times, etc and 
that's a good excuse to exercise my photographic skills too.

Once that's out of the way then can experiment with different discharge 
methods (attempting to prolong the "plasmoid"s' lifetime), since will be 
able to reliably instrument the process.

On Wed, 14 Apr 2010, Bert Hickman wrote:

> Hi Josh,
> 
> Very interesting images, including the others at:
> http://gallery.vandervecken.com/v/tesla/second-coil/capacitor-bank/axe-apr10/ 
> 
> As I understand your system, you're elevating the secondary base to several
> thousand volts DC via a small HV supply and using a 100 uF energy storage
> capacitor connected in series between the base of the secondary to RF ground.
> When the topload sparks to ground, it also then discharges the energy
> discharge capacitor through the secondary with a high current, low frequency
> (many 10's - 100 Hz) oscillatory "power arc" that may persist for 10's - 100's
> of milliseconds. The discharge current is limited by secondary winding
> inductance and resistance, and the dynamic resistance of the arc channel
> itself. Based upon the physical size of your secondary and arc length, this is
> likely 20-50 amps. The resulting arc-like discharges flow along the smaller
> spark trails initially blazed by the Tesla coil ground discharges.
> 
> In the top photo on the page you referenced, you're seeing several residual
> "plasmoids" left over from a recently extinguished arc discharge. These
> glowing regions are commonly captured in photos of high-power Jacobs ladders
> right after the arc "breaks". The other images were taken at earlier times
> during the high-current discharges where more of the arc plasma was excited.
> Some portions of the extinguished arc (constricted regions or sharp bends)
> don't cool down quite as quickly, and the thermally-excited air molecules in
> these regions continue to glow for a longer time than other portions. The
> hotter the original arc, the longer the plasmoid lifetime. These plasmoids are
> often observed in laboratory-created "ball lightning":
> http://www.ipp.mpg.de/ippcms/eng/presse/pi/05_06_pi.html
> 
> Similar plasmoids occur in "bead lightning", where regions of isolated glowing
> plasma remain for hundreds of milliseconds after the main stroke has ended:
> http://wvlightning.com/plains2005/june14h.jpg
> 
> BTW, be extremely careful - you have a true "killer system" there...  =:^O
> 
> Bert
> 

-- 
Josh Bailey (josh@xxxxxxxxxxxx)
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