design questions

List members,

  I am [still] in the design phase of my first distribution-xfmr powered 
coil. Only a few variables are fixed, and many are still undetermined. I 
have many questions to ask, and I'll limit myself to just a few in this 
post. Feel free to respond in private if you wish 

Here is what I have to work with:
- 19,920V 10kVA pig
- 10.5" x 44" coil form
- .04uF 40kV GE pulse cap

Here is what is proposed so far:
- #16 AWG magnet wire close wound 42" ???
- 5/16" copper tubing primary(flat), 1/4"-3/8" spacing, 12-20 turns
- hopefully a saturable reactor ballast
- RSG w/ 1/8" tungsten contacts

Here are a few questions:
If my toroid is, for example, 6" aluminum ducting wrapped around the 
outside of a plywood circle, about 48" diameter, what effect would 
covering the plywood with al foil have to the capacitance? WinTesla 
gives me 50pF for my proposed toroid capacitance, and I assume the 
actual will be higher with foil covered center. But how much higher? Any 
ball-park figures?

Also, the matched cap for my pig is .066uF. I am hoping that my .04uF 
will not be to great of a potential loss? I am pretty tight on my budget 
right know and buying a cap isnt what I want to do.

Finally, assuming that a will run the coil up to 10kVA(dont know if this 
will actually happen) I am not sure if I may need more pri-sec coil 
clearence. Is 2" sufficient between the coils or do I need more space?

I would really appreciate comments!
Tristan Stewart, KC2EBM

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