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[TCML] Connecting Vacuum Tube to TC and More.



Hello All,
This is my first post to the list.
I have a really elementary question, so please pardon my ignorance.
I am planning a Tesla coil with a flat spiral secondary for experiments with
X-ray and other vacuum tubes, especially Tesla's single-terminal "sensitive
brush" bulb demonstrated in his 1892 lecture. It was my intention to proceed
as I would with a normal Tesla coil and ground one end of the secondary
"pancake," while having the other end connected directly to the single
electrode of the small bulb, instead of the usual toroid. That is, instead
of figuring into the total secondary capacitance the capacitance of the
toroid, it was my plan to simply calculate the capacitance of the spherical
electrode and add this in.
However, upon re-studying Tesla's lecture before the New York Academy of
Sciences, it became apparent that the coils he used for his experiments did
not have a secondary ground connection, but had both their ends connected to
ball electrodes, like an ordinary induction coil. See, for instance, the
coil on page 41 of Anderson's edition of the lecture. If I am not mistaken,
in such a circuit the secondary capacitance would come solely from the
capacitance between the two discharge terminals (and of course the
distributed capacitance). What advantage is there to a coil of this form?
Also, would this type of coil be better for X-ray work as opposed to a
normal TC with a grounded secondary? Furthermore, how would one go about
connecting a single-electrode lamp, as opposed to a normal anode/cathode
X-ray tube, to this kind of coil? Would one terminal of the coil be
connected to the bulb and the other simply left alone? I guess what I'm
really trying to get at is this: could I carry out the plan described in the
above paragraph, and connect the free end of a grounded "pancake" secondary
to my single-terminal bulb, or is this an unconventional way of doing
things?
Another question I have is in regard to the actual secondary flat spiral
itself. Is there a formula, or could someone direct me to a book containing
a formula, for both the potential difference between turns (so that I can
calculate insulation) and for the distributed capacitance of a copper strip
flat spiral coil? I would prefer, if possible, to have the actual formula so
that I can perform the calculations myself, instead of using some Tesla coil
CAD program.
Thank you greatly for any help anyone can provide.

Joe Antonelli
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