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Re: Report on the latest activities

> The ball bearing gap provided about 20 small gaps, while my own 
> series gap provides 7 gaps.  My thought about this is that the 
> electrodes on spark gaps should be large and approximate a flat 
> surface.  Any thoughts anyone?

An electrode with a small radius produces a higher electric field at a 
given voltage than one with a large radius, so a small, pointed 
electrode would break down and conduct much easier than a large, flat 
electrode.  For example, at 15kV, a single gap with 2.5cm spherical 
electrodes would not break down until the gap length was .42 cm or 
less whereas needle electrodes would break down out to a length of 1.3 
cm (from the CRC Handbook of Chemistry and Physics).  Also, your 
small ball bearings might have heated up enough to maintain the 
ionized channel a lot longer than larger, cooler electrodes would have, 
letting the gap fire at a much lower voltage and transferring less energy 
to the secondary.

> The other interesting feature of last nights experimentation was that
> we noticed that many of the streamers seem to come out of one end 
> of the toroid, rather than being evenly distributed around the toroid.

I'm sure there are a lot of things that determine where the streamers 
actually break out; but I would assume that they generally follow the 
lines of highest electric field intensity.  You might look to see if there 
are any large conductive/magnetic objects in the direction preferred by 
the streamers that could be distorting the field (a refrigerator right 
upstairs, etc...)?  Also, if you just turned or moved your entire coil 
assembly and the streamers turned with it, you could probably assume 
that it was some asymmetry associated with your coil and not the 
environment.  I noticed that my coil would usually fire off towards a 
metal plate I have on my wall (which was fairly close) rather than 
radiate out in all directions.


Steven Roys (sroys-at-radiology.ab.umd.edu)