Re: CD capacitor

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

Original poster: "Herbert Mehlhose by way of Terry Fritz <twftesla-at-qwest-dot-net>" <herbert.mehlhose-at-kdt.de>

Hi,
some thoughts to your question:
1. CD's are made of Polycarbonate, about 1.1 mm thick.
The information (pits) are embossed and a very, very thin! layer
of aluminium is applied to this surface. For protection, a layer of paint
is applied. (That's why a CD is in fact more sensitive on the print side
than on the side facing the laser).
I don't have an idea how to remove the paint without destroying
the aluminium layer.
2. The currents in use for a tesla coil primary maybe could be
too high for the thin aluminium layer. And how could you make the contacts
for the stack? The CDs must be pressed together, which means that the
contact material must be as thin as the aluminium layer itself.
3. The dielectric constant of PC is about 3 (LDPE about 2.3),
dielectric strength is about 380kV/cm (similar to LDPE), but the
dissipation factor at 50Hz is 0.7, at 1MHz it is 10.
The dissipation is higher than LDPE and PP (PP is 0.5 at 1MHz), and it
is too high for typical tesla coil use with frequencies of about 100kHz and
more.
4. If you stack the CDs, there will be not enough space between the
aluminium layers. This will result in breakthroughs between the layers.
5. A cap ot this type also would need to be submerged in oil. Not sure, if
PC will withstand oil.
Conclusion: construction would be difficult and losses are too high,
in my opinion CDs are not well suited for TC use.
Happy coiling,
Herb