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Re: What it takes to get big sparks?
> .............................It must be noted that all leaders are
invisible,
> low current ionization paths. The arcs move out along the multiply
restarted
> leader paths over time spans from 50 to 500 milliseconds for long arcs.
In
> the
> long time scale, late in full arc development, the leaders grow more from
the
> ends of the ever advancing arc channel that the terminal.
>
True, but that leader has to get there, even if it only faintly luminous.
And, it needs charge to propagate at the required rate. If there isn't
enough charge (or stored energy quickly available), the leader doesn't
propagate. It seems, from my reading, that there isn't anything such as a
"slow leader".. Either you get one long fast leader (when there is enough
charge behind it), or you get a succession of little short ones,
continuously forming and collapsing, as the charge moves out into the
leaders and back to the electrode. The limiting case for the latter would
be a brushy corona discharge.
So, perhaps it is really two processes, with differing requirements (hence
the non-trivalness of getting big sparks from a TC):
1) Formation of the leader (slightly luminous), very fast, requires enough
charge and a low inductance source (i.e. the top load)
2) Development of the visible arc: requires enough energy to make the air
hot enough to conduct, and luminous as a result, occurs much slower, and
can take power through a relatively high inductance source (e.g. the
secondary coil).