Re: Sparks - Bright in the middle, how to verify it.

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

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <paul-at-abelian.demon.co.uk>

Charles Hobson wrote:

> At the center of these sparks there is a 25mm segment which
> is much brighter than the rest.

Interesting. Never noticed that myself. 

Jim Lux wrote:

> Sparks tend to grow from one polarity better than the other.

Seems like a reasonable explanation. Ought to be easy to
demonstrate.

In response to the various suggestions, why not use a photo
detector, or a pair, suitably collimated, and compare their
outputs with the top voltage waveform. A suitable choice of
detector should give a frequency response adequate to follow
the variation of the arc's light curve at the RF frequency and
allow comparison of the alternate half cycles. I suggest that
this simple method might give informative results.

Eg,

(fixed width font)

 terminal           arc               terminal
  >>>>> \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/ <<<<<


                      | 
                      |collimating 
                      |screen
                      |
            \    /    |    \    /
             |__|     |     |__|
              D1             D2
                 photo detectors
                                         *******           
                                      ***       ***        
                                   ***             ***     
                                  *                   *    
                                **                     **  
                              **                         **
-----------------------------*-----------------------------
**                         **                              
  **                     **                                
    *                   *                                  
     ***             ***                                   
        ***       ***                                      
           *******                     
^^ Top volts ^^

                                         *******           
                                      ***       ***        
                                   ***             ***     
                                  *                   *    
                                **                     **  
                              **                         **
**-------------------------***-----------------------------
  ****                 ****                                
      *****************                                    
^^ D1 output ^^       

                                    *****************      
                                ****                 ****  
-----------------------------***-------------------------**
**                         **                              
  **                     **                                
    *                   *                                  
     ***             ***                                   
        ***       ***                                      
           *******     
^^ D2 output ^^

It would be quite interesting to look at the light curves of arcs
under various operating conditions. Does anyone know of any existing
results? I don't suppose they are sinusoidal as I've shown above -
they might start with a sudden peak as the stored charge is released,
followed by a gradual decay.

Cheers,
--
Paul Nicholson,
Manchester, UK.
--