More on sparks--& AOL's goofs

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

Original poster: "K. C. Herrick by way of Terry Fritz <twftesla-at-qwest-dot-net>" <kchdlh-at-juno-dot-com>

I'm back with Juno for this one.  I found that I never received, via AOL, Bert
Hickman's posting of 26 April or John Freau's of 27 April.  I remember also
that back in March I hadn't received a couple of List postings regarding my
goofy spark-booster idea.
 
I did receive Bert's 4/25 posting but forgot that I''d wanted to comment as
follows on that:
 
This is not to put Bert on the spot or even to ask him for more
explication...but the quote he gave from Raizer somewhat baffled me.  Perhaps
it's because I learned my college EE and physics, such as it was, half a
century ago; or perhaps it's because maybe English is not Raizer's first
language...?
 
"The avalanches at the _rod anode_ travel to it from the outside; as
they come nearer, they enter the region of progressively stronger field.
This factor _facilitates_ the multiplication of electrons and
_stimulates the avalanche-streamer transition_. In the case of the _rod
cathode_, multiplying avalanches move further from the electrode into
the region of progressively weaker field. The multiplication process is
therefore _slowed down_ and the _avalanche-streamer transition is
inhibited_. Moreover, in the case of the positive rod, electrons sink
into the metal, leaving behind a noncompensated positive space charge,
which enhances the field at the electrode. In the case of the negative
rod, however, the field of the corresponding negative space charge is
somewhat compensated for by the field of positive ions, all of which
stay in the gas." 
 
1.  Firstly, I don't appreciate what the physical configuration of the
electrodes is (but perhaps Raizer disclosed that elsewhere in his paper). 
Also, how that configuration would relate to a typical Tesla coil
configuration.
 
2.  1st sentence, "...travel to it..." and "outside": unclear to me exactly
what is meant.  And in fact, "avalanch" itself: is that a process, a phenomenon
or a physical entity?  (Right off, I'm sure many of you can now assess the
extent of my knowledge!)
 
3.  2nd sentence, "...multiplication of electrons":  where do the electrons
come from?  Does "multiplication" perhaps mean "incorporation of more"?
 
4.  Next sentence, "...multiplying avalanches move further...": what means it,
"multiplying": "becoming bigger"?..."becoming fatter"?..."becoming more
numerous"?  And what means it, "move further": moving to a different
location?...extending in length?...?
 
5.  If I understand the "Moreover..." sentence correctly, that one would seem
to be the most pertinent:  He seems to say that regardless of the electrode
polarity, there's always in existence, at that electrode, a positive
space-charge.  When the electrode is positive, that charge adds to the field
and when it's negative, it subtracts.  Showing my ignorance again, is that the
case?
 
Bert, as to your 26 April posting (beginning, "The breakdown sequence..."),
allow me to say this about that:
 
1.  Mea culpa again:  I don't appreciate exactly what "avalanch", "streamer"
and "leader" mean.  If you should be inclined to say to me, "Go read a book", I
will fully & completely accept that--& maybe I will.
 
2.  Other than that, your posting is admirably clear to me.  It confirms my
general understanding that the smallest effective radius of curvature, of a
conducting surface that is a part of a closed high-voltage system, is the
location from which a spark is going to originate.  But there seem to be
qualifications associated with that general rule--as to polarity, size and
shape of other such surfaces in the system, the nature of intervening gases if
any, etc., that remain unclear.
 
As to John Freau's 4/27 posting (beginning, "I was thinking some more..."), 
 
1.  I can, without too much trouble, and will, modify my s.s.t.c. system for
cycle-counting:  I will put in a switch-selection for pulse-burst lengths of
64, 128, 256, 512 and 1024 excitation-cycles.  That's from the beginning of the
ring-up time.  Ring-up to break-out will still take about 30 cycles, at 140
KHz.
 
2.  When I had written previously that I'd had an interrupted-burst mode of 64
cycles on, 64 cycles off, etc., I should have said 128 cycles (& I made that
mistake once before); my gate signal was taken from the Q7 output of a CD4020,
and 2^7 is 128, not 64.  I'm going to replace that IC with a CD4040.
 
3.  Due to circuit considerations, I'll no longer be able to have that
interrupted mode.
 
4.  I'll still be able to operate at any sub-multiple of the max. 120 Hz
spark-rate.  Later, perhaps I'll beef up my low-voltage supply (for the MOSFET
gates) so that I can fire the coil asynchronously & so at a higher rate than
120/second.  Once I do that, I'll really be able to tweak the duty cycle of the
sparking & see what happens.
 
5.  I'll repeat my observation that, when I did have that interrupted mode
operative (128 cycles on, 128 off, etc.), I noted that the probe-sensed
field-voltage a) dropped (close) to zero during each off-time and b) resumed at
the same level at the end of the off-time.  In other words, it did not
appreciably rise, toward what it was before the initial spark break-out, during
that off-time.
 
6.  For now, I think it most likely that John's phrase, "permit higher voltages
or currents to be utilized" is the key to longer sparks.  Get all that power up
front & cram as many electrons into the electrode as you can, as fast as you
can.  Ring-up in 2 cycles rather than 30.
 
Ken Herrick