Re: Vortex gap loss measurements

["Daniel Boughton" <daniel_boughton-at-yahoo-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Malcom:

It is obvious that the gap cannot be described via
linear resitive model(see my additional comments to
Gary). Plasma is a very unique thing. I have worked
for years with RF generators, impedance matching
networks to plasma chambers for silicon etching. With
a rich variety of gas mixtures, pressures,
temperatures, volumes, and frequencies a wide variety
of impedance responses are dynamically encountered
(primarily capacitive). The matching networks are
automated to analyze the load (chamber) impedance by
detecting the foward and reverse VSWR and adjust the
capacitors (vacuum variable) for max power transfer.
The chamber was in a constant flux (as far as
impedance goes) when ignited. Even so, a mathematical
model of behaviour was derived which acurately
predicted the behaviour across all variables. This
mathematical model was loaded in the firmware to
automate the match. The result was to have precise
tuning in a very fast time response (due to
microprocessor calculation speed and servo motion to
adjust the capacitor).

I say all of this for a few reasons: (1.) a linear
resistive model cannot purely describe the development
of plasma in the gap as you pointed out. (2.) I do not
believe that any mathematical model of a single static
gap under an air blast of quantified pressure has been
developed to date which adequately describes and
predicts plasma behaviour in the gap. The circuit
(external to the gap)response has been the only point
analyzed to date (see Morecroft). (3.) Treating the
primary RLC circuit as a lumped element analysis falls
woefully short of any real description of circuit
phenomena and must be described as distributed.

I have found that my rotary spark gap with about 8KW
powering it is a tremendous broadcaster of EM energy.
The metal shielding I have in my lab actually has
plasma balls about 1 cm in diameter form in the cracks
between them when running off tune (no sparks issuing
from the secondary). The math model must also account
for this radiated power loss. Treating it as a lumped
element ignores other richer gap phenomena as well.

Now as to a linear decrimenting model, the equation
for it is quite easy to develop given Gary's data
(simple 1st degree equation and we know the envelope
and intercepts so a simple direct variation RT
equation will account for his data if you haven't
already see his scope images) but the gap phenomena as
a circuit controller is much more complex. For
instance the arc has its own inductive elements as
well as capacitive (how much energy is stored in the
magnetic field of the inductance and how much in the
electrostatic field of the capacitance and what is the
resultant impedance? How does impedance change as a
function of time? Does it swing from capacitive to
inductive? Does it resonate at its own (assumably high
frequency and how does this impact the operation of
the circuit). Now it is quite clear that if you force
an RLC response the circuit will respond to the
logaritmic equations (any 2nd year EE student will
have done this experiment in lab and derived the
equations). One experiment might be to use a plasma
tube in place of a gap under strict controls and
monitor the conductance (and admitance) of the plasma
(although RF plasma engineers have been doing this for
years) as the variables are processed. 

You noted in your message that "The gap is dissipative
but that is where the similarities with resistance
end. I analysed this and wrote a note on it several
years ago." How do you mean dissipative? Do you mean
heat loss? Secondly, don't take me wrong (I agree as
you can tell from my previous statements) but how did
you determine that the gap (I think you mean arc)is
dissipative and that is where similarities end? How
did you conduct your experiment and do you still have
data?


Regards,

Dan

--- Tesla list <tesla-at-pupman-dot-com> wrote:
> Original poster: "Malcolm Watts"
> <M.J.Watts-at-massey.ac.nz> 
> 
> On 2 Sep 00, at 18:36, Tesla list wrote:
> 
> > Original poster: "Daniel Boughton"
> <daniel_boughton-at-yahoo-dot-com> 
> > 
> > Gary:
> > 
> > This is a very interesting experiment. First, when
> you
> > measured the slope during the ring down, did you
> see
> > the same size decrement of each succesive
> oscillation?
> > Is this what you mean by linear as oppossed to
> > logarithmic? Traditional wisdom purports that the
> > decay is according to V(t)=V(i)e^-rt where V(i) is
> the
> > forced initial potential on the capacitor. Your
> > results are very interesting however in that it
> flies
> > in the face of convention. The derived equation
> must
> > be something like V(t)= V(i)*-krt. I wonder if
> without
> > the secondary it is linear due to resistive losses
> > only. Without the secondary the additional
> absorption
> > of energy via the secondary mutual inductance is
> > missing which accounts for the linear decay? Also
> what
> > I found interseting was that with the gap distance
> the
> > slope remained constant. I would have expected
> greater
> > gap resistance at further distances but it seems
> that
> > the plasma provides a constant resistance no
> matter
> > how wide the spark gap is set (within reason of
> > course-I 'm sure at a foot the resistance would be
> > substantial as compared to 300 mil).
> 
> The linear decrement of a ringing RLC circuit which
> has a gap 
> in series with it was discovered by Stone circa
> 1914. The 
> Corums mention it in their literature but
> unfortunately never 
> went on to use the information in their modelling.
> The linear 
> decrement is entirely due to the gap
> characteristics. An RLC 
> circuit by itself produces only a logarithmic
> decrement. This 
> clearly shows that modelling the gap as a
> resistancwe does not 
> work. You cannot apply the classic time constant
> equations to 
> this situation. The gap is dissipative but that is
> where the 
> similarities with resistance end. I analysed this
> and wrote a 
> note on it several years ago. It is important to
> note 
> (ultimate pedantry) that you *cannot* ascribe a
> value for Q to 
> the primary if the primary includes a gap. You can
> compare 
> various primaries with each other by comparing the
> ringdown 
> slope (gentler is obviously better).
> 
> Regards,
> Malcolm
> 
> 
> 
> 


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