Re: Superconducting tesla coil...

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Jim Lux <jimlux-at-earthlink-dot-net> 

Phenolic/canvas is fairly low loss for RF (it's used for coil forms, tube 
sockets, etc.)  I don't know that I'd want to use it for X-band microwave 
stuff, but for <30 MHz, I doubt you'd have to worry.

Carl von Linde first liquified air in 1895.  When was Tesla fooling with 
liquid air?

And, for what it's worth, liquid air can be kind of hazardous... the 
nitrogen boils off leaving liquid oxygen behind.  Worse yet, the oxygen 
condenses out of the air as the nitrogen boils.  LOX and combustible 
materials -> serious fire hazard..

These days, cryo insulation in NASA test equipment is expanded polystyrene, 
silica foam, PTFE foam, or vacuum jackets..  We also use a lot of stainless 
steel (which is fairly low thermal conductivity... so, for instance, you 
can get semirigid coax with stainless steel jacket and center conductors, 
plated with a thin layer of silver (skin effect is your friend).  And, 
there's always composites of one sort or another.

And, for the totally cool and sexy insulation, there's aerogel (available 
commercially if you want to play around... google for it..).  We use 
aerogel for insulating the rover electronics boxes from the Martian night 
(both Sojourner and the two MERs).


At 08:32 AM 10/3/2003 -0600, you wrote:
>Original poster: "Harold Weiss" <hweiss-at-new.rr-dot-com>
>Hi All,
>
>In this case, a phenolic form would be useful.  A year ago at EAA, the NASA
>guys were demonstrating LN2 on flowers,  balloons and bananas.  I had a
>small chunk of canvas phenolic and we dipped it in.  It didn't get brittle.
>The rep told me that they use the stuff for insulating cryo lines in test
>stands.  Might work for a SC coil.  The only problem might be the RF losses.
>They might eat up any benefits.  I remember reading somewhere, that Tesla
>did have a liquifer and did play with a liquid air coil. (pre lab fire)
>
>David E Weiss
>
> > Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com>
>
> > Plastic becomes very brittle even at zero degrees F.  You might crack your
> > coilform depending on its material.
> >
> > Dr. Resonance
> >
> >  >
> >  > LN2 == Milk as far as cost goes... $.50/liter... $100 gets you a big
>GP45
> >  > dewar (that's 45 gallons, folks)
> >  >
> >  >
> >  >
> >  >
> >  > >  But I'd want to be
> >  > >careful that my components have similar thermal expansions. Use
>something
> >  > >with a large theremal expansion coefficient as your winding on
>something
> > that
> >  > >doesn't, and you'll get broken/stretched wire as the wire shortens and
> > tenses
> >  > >up.
> >  >
> >  > Precisely the problem you'll have... particularly things that are
>plastic,
> >  > aren't when cooled to 77K...