Re: Marx generator (fwd)

["High Voltage list" <hvlist@xxxxxxxxxx>]

Original poster: Steven Roys <sroys@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Wed, 23 Nov 2005 14:15:12 -0700
From: Gomez Addams <gomez@xxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: Marx generator (fwd)


On Nov 22, 2005, at 1:35 PM, High Voltage list wrote:

> Original poster: <sroys@xxxxxxxxxxxxxxxxx>
>
>
>
> ---------- Forwarded message ----------
> Date: Tue, 22 Nov 2005 10:33:54 +0100
> From: Herwig Roscher <herwig.roscher@xxxxxx>
> To: High Voltage list <hvlist@xxxxxxxxxx>
> Subject: Re: Marx generator (fwd)
>
>
>
> Malcolm Watts wrote to the High Voltage list:
>
>> In theory, mine should have been 250 - 300kV when
>> erected. I got about  7" sparks.
>
> Hi Malcolm,
>
> This is 0.023" / kV. As my system produces 0.027" / kV, I'm in the
> ball park  :-)
>
>> Gap settings are rather critical.
> For a loading voltage of 20 kV, I set all spark gaps to 0.28". This
> is enough not to cause any premature ignition. The spark gaps consist
> of brass balls of 0.04" diameter. IMO any larger distance would
> increase the losses unnecessarily - correct?

Ball size should have no impact on gap losses once a gap fires.

I am very surprised that spheres that small are holding off 20kV over a
distance of only .28".  Are you quite certain your stages are charging
to 20kV?  You've measured with a HV probe?

>> Ideally the it should erect from bottom to top. I didn't bother with
>> triggered gaps.
> Using a trigger should ensure, that the erection will start from the
> bottom. The optic impression(sic!) is that the erection runs upward
> correctly.

Another trick in Marx bank design is to ensure that all the spark gaps
have a clear "view" of each other (spark area to spark area), such that
none of the spark gap electrodes "shadow" any of the spark area of an
adjacent spark gap.  This provides for UV illumination from a gap to
partially pre-ionize the next gap, and has been shown to dramatically
reduce the erection time of a Marx bank, as well as to improve the
consistency of erection times from shot to shot (jitter).