[TCML] Magnifier topics

[Paul Nicholson <tcml88@xxxxxxxxxxx>]

David Sharpe wrote (in another thread):

> I suspect the connection you are alluding to is that the
> "driver secondary + transmission line" acts as a 1/2 wave...

> If that is true, an electrical high stress "node" would
> (should) appear mid-way up the driver secondary.

Yes.   Actually there are two 3/4 wave modes coming into play!

The lower frequency one has a 1/2 wave spanning the secondary, a
voltage node (zero) on the transmission line, and the tertiary +
topload makes up the remaining 1/4 wave.  This is the resonance
you describe.

But there is another 3/4 wave mode present too, at a higher
frequency.   This one has 1/4 wave along the secondary, a
voltage antinode (max) coinciding with the transmission line
and the tertiary + toroid spans the 1/2 wave, with a voltage
node (zero) somewhere inside the tertiary.

These two resonances correspond to the 2nd and 3rd frequencies
of the tuning mode 1:2:3 described in lumped terms by Antonio.

How do we support two 3/4 wave modes?  Well the primary
coupling separates them - they have opposite polarities of
primary voltage.   Strong coupling to the secondary is required
to achieve this state of affairs.

The three (or more) resonant modes, tuned appropriately, can
be arranged to momentarily cancel out some of the internal
voltages at a point in time coinciding with max topvolts.
Ideally, at this instant, all the induced voltage is across
the tertiary.  The result is a higher top voltage for a given
bang energy compared with what can be achieved by a 1/4 wave
resonance alone.

Antonio has covered this stuff pretty thoroughly but I like
to describe it in the language of distributed resonators.
There is some interesting physics involved, especially with
the concentration of primary coupling onto the secondary.

We should call this the 'modern' approach to magnifier tuning.
Prior to Antonio's fairly recent work, I don't think the
interplay of multiple resonances was ever considered.

There are many open questions, and some things that are
theoretically sound but which have not been confirmed by
coilers.

It is usually accepted by coilers that 3-coil systems can
outperform a 2-coil system (or at least, they can stand up
to more power?)  but it has not been confirmed experimentally
that multi-mode tuning is the reason for better performance.
There are other factors and possibilities.  For example,
splitting the resonator into a secondary and tertiary and
applying strong coupling to the secondary will produce a lot
more overtone content - for geometrical reasons.   Do these HF
components contribute to streamer channel heating?   Hotter,
brighter breakout would be a general result, not requiring
specific tuning of the overtones.

This is a great area for research.  The topic hasn't been
discussed in anger since 2003 which is why I take the
opportunity to bring it up.

Shannon wrote:
> It would be great to add some fundamental knowledge...

I will post some notes in a day or two - I want to run some
animations which will make things clearer, I hope.   It would
be great to inspire some expert and well equipped experimenters
to investigate 3-coil systems in meticulous detail.
--
Paul Nicholson
--
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