Re: New Capacitor (and a question about bombarders)

["Tesla list" <tesla-at-xxxxxxxxxx>]

Original poster: "Bert Hickman" <bert.hickman-at-aquila-dot-net> 

Tesla list wrote:
> 
> Original poster: Tesla729-at-cs-dot-com
> 
> Hi, Fellow Coilers,
> 
> I just received my .22 uFD -at- 50 kV Maxwell pulse cap that
> I won off of ebay today. It was supposed to have come out
> of a Marx generator bank from Los Alamos Labratories. It is
> amazingly small considering its voltage/capacitance comb-
> ination ( 11 3/4" long X 5 7/8" wide X 2 3/4" thick ), but is
> quite heavy for this size, too (~15 lbs). It's suppoesd to have
> .93 uH equivalent series inductance ( I'm assuming that that
> is quite low, which is good?) I determined its actual measured
> capacitance to be .211 uFD. I figure this is enough capacitance
> to handle one monster of a Tesla coil ( like Kevin Eldrege's
> "Biggg Coil"), but may have to incorporate a series/parallel
> configuration of 4 for the same capacitance -at- 100 kV to safely
> handle the required voltage and current levels for such a system.
> 
> Now to my bombarder question. I've heard of using pig-like
> transformers to "bombard" a bank of NSTs, but I really don't
> understand exactly what this is referring to. If it's not getting
> too much off topic, maybe some of the engineers on this list
> could enlighten me concerning this ;-]
> 
> Keeping 'em Sparkin in Memphis,
> David Rieben

David,

Based upon the small physical size of the cap, it MAY actually be a
Mylar energy storage cap... Maxwell makes both types, and the low duty
cycle of a Marx generator does not require the low RF loss
characteristics of a Polypropylene cap. Do you happen to have a Maxwell
part number? 

A bombarding transformer is simply a high voltage transformer (up to 24
kV or so) that can deliver considerably higher current than an NST (from
many hundreds of milliamperes to over an ampere for larger tubes and
electrodes). The transformer can be a true bombarding transformer sold
by a neon sign supply house with either self-ballasting or an external
inductive or magnetic amplifier ballast. Or it may be a "home brew"
setup using a power distribution transformer with an external inductive
ballast. A bombarding transformer is typically sized at 10 - 22 KVA.

The idea behind bombarding is to use high current to generate
significant heating of the electrodes and glass tubing. This forces
outgasing of absorbed gases or surface impurities prior to backfilling
with rare gas and final sealing operations. In practice, the glass
tubing is heated until it will scorch paper, and later on in the process
(at lower gas pressure) the internal electrodes are heated to red heat.
If not done properly, adsorbed impurities inside the tubes will slowly
outgas in use, resulting in premature failure - flickering or even a
failure to ignite. 

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com