Re: Capacitor design and Toroids

In a message dated 96-02-28 15:16:01 EST, you write:

>Hi All
>I have started building a REAL coil. 8"dia 26" long secondary and would
>like any feedback to keep the project on track.
>Has any one used Kapton for the dielectric of a capacitor?
>This stuff seems incredible with specs like..
>dielectric strength of 7000V/mil
>dielectric constant of 3.5
>and dissipation factor of 0.003 at 1KHz?
>Also I thought I would make a toroid ~ 4" x 12". My question is if
>the center needs to be removed or can it be shaped like a
>fat disk, (that is a 4" thick disk with rounded edges?)
>I brought my secondary into work to measure it to see what numbers I get
>to compare to the calculated values. I will disclose the results when
>By the way I work at Fermilab which does high energy physics. I have worked
>in the past as a technician in the RF section and worked on 200KW 30-50Mhz
>systems. I had the opportunity to witness a 30MHz Tesla in action. This was
>quarter-wave high power transmission line (about 8" outer conductor with 3"
>inner heavy
>copper) with a 300Watt solid state amplifier driving the current end, about
>from the shorted end. When properly tuned the open end would have a very
>nice plasma about an inch tall coming off the center conductor. If touched
>it would leave white ash as the skin surface was destroyed. It was quit an
>interesting sight. 
>I also lite a 60W incandesent bulb off the end by holding the screw portion
>of the bulb
>tightly with my hand an touching the center conductor to the bulb completing
>the circuit.
>The only sensation was the heat from the filament.
>Dave Huffman


Have you checked the price on Kapton?  I think it may be prohibitively
expensive.  It is a great material for capacitors.

I am sure the toroid you described would work fine.  Most home built toroids
are circular on the outside and flat in the center because it is the easiest
way to make them.  Your 12" toroid will be ok for getting the system up and
running but with an 8" dia. secondary, you will want a much larger toroid -
like 30" or 40" or larger.  I am presently using a 40" toroid on my 6"
secondary at 5 to 8 kva.

It sounds like you have the job most of us would like.

Ed Sonderman