Re: What it takes to get big sparks?
Tesla List wrote:
> Original Poster: "Jim Lux" <jimlux-at-jpl.nasa.gov>
> 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).
Now you are in full understanding of what really takes place in the
from the TC. I noted in a post about two months ago that the initial
ionization (leaders) occurs in the 2-20usec time frame. Arcs grow slowly from
power fed over time into the pre-ionized path. Bulk ionization from flaming
white arcs takes a number of milliseconds to recombine. (thousands of times
longer than that initial low current leader ionization). During the dwell, or
off time of the TC, this starts to happen, but with a moderately rapid rate of
break, enough residual ionization remains so that the next impulse's leader
zips instantly, expending little charge energy along the remenant ionization
channel. Left over leader energy forges out farther still and the energy from
the system lights the newer, longer channel to white heat. This continues
until the arc length approaches some value where the the old ionization
presents enough difficulty for the fixed leader charge to maintain the arc to
that length only.
Richard Hull, TCBOR