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Re: oil filled resonators

Hi Robert, all,

> I'm in the process of building a large vacuum tube driven TC for a
> commercial client right now.  Last year I fabricated an oil filled
> resonator for this project consisting of a 16 inch diameter
> fiberglass form close wound with #8 AWG thermaleze copper wire to
> a length of 5 feet. This coil is positioned coaxially inside a 200
> US gal steel cylindrical drum and filled with VoltEsso 35 oil.  A
> large oil filled shedded ceramic bushing (12 inch outside diameter
> and 30 inches long, 8 inch oil filled hollow around a 1/2 inch
> copper waterpipe HV buss inside) sticks vertically out the top side
> of the horizontal drum at one end making it look like the
> smokestack on a steam locomotive.  A spun aluminum terminal tops
> the bushing as the HV output.  Inside at the other end is a 15 turn
> flat copper ribbon spiral primary.  I have little test time on
> this device as yet, and only with a modest vacuum tube exciter
> oscillator.  I am not generally pleased so far with the Q which is
> lower than from a similar coil in air and without metal walls
> around.  Note also that the surrounding metal container is lossy
> mild steel, not silvered copper.  There should be both eddy
> current as well as I2R losses in the skin depth.  Operating
> frequency is 100 kHz. 

I'd be inclined to try a non-conductive container if poss. If wall
conductivity is anywhere between perfect and zero, it will lose a
lot of energy. Be interesting to work out the wall impedance where
this reaches a maximum. Also, you'll end up with a lot more 
distributed C than is desirable. The Q of Abramyan's container-
enclosed accelerator was rather poor (about 70 from memory) despite 
silvered walls. The other thing is that the primary is going to
have an uphill battle due to interference from the more-or-less
shorted turn surrounding it. Also, have you thought about using much 
higher k's since the coil is oil-immersed?
    Could someone please post on what plastics are resistant to attack 
from commonly used oils?

Malcolm