Re: marx chokes

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

Hi DC,
       From memory it was several mH per choke. For the first
machine, I used 0076-type PVC-coated hookup wire wound in three
layers over a rod about 1/4" in diameter and about 5" long. Each
capacitor was a homerolled dry-fired poly/foil cap wound as per the
recipe in my article except that there was no acrylic former in the
centre. Each was about 5 - 7 nF as I recall. The machine is difficult
to describe but was designed to be as short as possible for the
voltages to be developed. The tower formed (looked a bit like a
highrise) was about 20" high, maybe a bit more.
     Each stage was sandwiched between two acrylic sheets with two
thick lumps of acrylic to generate the spacing. The gaps were formed
from heavy copper wire. It is really difficult to describe. I did
take some pictures though. I'll have to wade through rolls of
negatives and get some prints to scan. It would be much easier to see
than describe. The first machine had about 20 stages and the second
had 22. The chokes for the second machine were made using the same
rods but with a single layer of polyesterimide wire wound over a
coating of insulation tape and the inductance was lower. The first
machine worked better and reflected the higher choke inductance and I
think would have worked better if the inductance had been higher
still. It was charged using a flybaack cap charger (my test EHT
supply) to about 15kV/stage before it erected. I used no triggering
gap but it wasn't difficult to adjust the gap spacing so it worked
reliably. I got the idea after trying out the Blumlein switch shown
in an old Amateur Scientist article which showed it being used in a
pulsed UV laser. I later procured a copy of Sargeant and Dollinger's
"High Power Electronics" and saw that my "novel" design had been
thought up and developed decades earlier. I will get some pics
sometime over the next week and ask Terry nicely to put them in my
little corner of his website ;)

     A word of warning - first light was a great success but resulted
in my spending the next three days repairing a variety of equipment
which had been taken out in the workshop in which I tried it. I think
the main problem was inadvertently applying high amplitude step
functions to the mains ground but I wouldn't be afraid to take a bet
that it wasn't a bad EMP generator in its own right. Thereafter
running was confined to a physics lab. The topology of the structure
resembled a helical antenna with gaps forming a spiral in one
direction and chokes forming a spiral in the other. I can only guess
at the electrical mayhem that went on when it erected.

Malcolm

On 11 Apr 2005, at 23:18, Tesla list wrote:

> Original poster: "Dr. Resonance" <resonance@xxxxxxxxxx>
>
>
>
> Malcolm:
>
> What was the value of your chokes?  I would like  to try this idea as
> well. Digi-Key stocks a large number of iron core chokes.
>
> Dr. Resonance
>
>
>  >
>  >
>  > Use chokes instead of resistors. The benefits: much faster and more
>  > efficient charging (far less resistive loss). As to the values, >
>  mileage varies. There is balance between charge time and sufficiently
>  > high impedance at discharge time. I built two working Marx banks, >
>  both of which used chokes wound on ferrite rods. I spoeculated at the
>  > time that suitably sizing the components might allow resonant >
>  charging at mains or some other nominated frequency but pursuing the
>  > idea is way down my list of things to do. > > Malcolm > > >
>
>
>