Re: Ceramic Tank Circuit Caps

To: tesla-at-pupman-dot-com
Subject: Re: Ceramic Tank Circuit Caps
From: Ed Phillips <evp-at-pacbell-dot-net> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
Date: Mon, 12 Oct 1998 22:50:30 -0600
Approved: terryf-at-verinet-dot-com

Tesla List wrote:
> 
> Original Poster: Gwyn Zucca <gwyn-at-tcbod.demon.co.uk>
> 
> Hello All,
> 
> I have been having some off list discussions regarding using high Q, low
> loss RF/power ceramic caps in the primary circuit. These caps would be
> the type of thing used in high rep rate pulsed laser/ RF work.
> 
> We have tried using these capacitors on small TCs with the caps in oil
> with good success, this type of ceramic cap gives a very sharp pulse.
> 
> Has anyone else been using ceramics?
> 
> Any comments or ideas welcome.
> 
> Cheers
> 
> Gwyn D Zucca, TCBOD, ENGLAND

	The high Q, low loss RF/power ceramic capacitors are very expensive,
and have low capacitance per unit size.  I and a number of others are
using HV ceramic capacitors intended for power supply filter work. 
(0.0047 mfd, 20 kV for example).  They have pretty low series resistance
and work fine for a few seconds, but then begin to overheat due to
dielectric loss and, at least in my experience, fail after a few
minutes.  Because of their very low inductance, these same capacitors
are indeed used in ultra fast high power Marx generators, but at a very
low repetition rate.  I use them because they (were) very cheap and do
work fine, with all of their limitations.

Ed