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Re: Triggered Spark Gap



Original poster: "Shaun Epp by way of Terry Fritz <twftesla-at-qwest-dot-net>" <scepp-at-mts-dot-net>


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, November 10, 2001 9:59 AM
Subject: Re: Triggered Spark Gap


> Original poster: "Luc by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<ludev-at-videotron.ca>
>
> Hi Kelly & Phillipa,
>
> I need to remember not to start my post by "Hi guy" any more we
> have a women on the list now ;-) welcome.
>
> Some commercial trigger gap are trigged by light, most of the
> time they used only an open arc near the main gap.
>
> Cheers,
>
> Luc Benard
>
> Tesla list wrote:
> >
> > Original poster: "Kelly & Phillipa Williams by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <kellyw-at-ihug.co.nz>
> >
> > Dear All,
> >
> > While reading my physics textbook this week I came up with a really
neat, if
> > fairly esoteric, idea for a triggered spark gap.
> >
> > All metals have a certain energy barrier preventing electrons from
leaving
> > the surface of the metal. (Analougous to a rounded curb at the edge of a
> > flat road, it keeps a slow-moving soccer ball on the road unless it is
> > kicked hard enough.) This energy can be provided by heating the metal
very
> > hot (thermionic emission),
> >
> > Or by bombarding the metal with photons (light) of a high enough
frequency
> > so that when an electron on the surface absorbs a photon, it jumps off
the
> > metal.
> >
> > Now suppose an enclosed spark gap in a box, surrounded by an xenon
> > flash-tube or similar source of light.
> > The electrodes a slightly too far for the voltage to jump alone, but
when
> > the tube flashes and the electrons jump off the metal they ionise gas
and
> > fly across to the other electrode, thus initiating the spark. I know
this
> > effect occurs in a slight vacuum, but I would have to investigate it's
> > effect in air.
> >
> > The only problem is that the cut-off frequency for this emission for
many
> > metals, and tungsten too I would imagine, is in the ultraviolet range
and
> > slightly above.
> >
> > Could those with a working knowledge of x-ray tubes tell me whether an
x-ray
> > tube can be PULSED at 100 (50 Hz)
> > or 120 (60Hz) to trigger a gap like this? Forced air quenching may also
be
> > necessary, although this technique could be applied to a single static
gap
> > all the way through a multi-gap-static-gap, provided the metal of the
gap
> > itself was exposed.
> >
> > I would very much appreciate knowing whether vacuum tubes can be
pulsed -
> > maybe a pulsed supply to the x-ray tranny, would that work?
> >
> > Best Regards,
> >
> > Alan Williams


Hi Alan,

I've taken some X-ray tube theory in College (Medical Electronics) and I've
taken x-ray heads and Power supplies apart, so I'm some what qualified.   My
suggestion is DON'T DO IT!! unless you have the Heavy (mechanical
construction and physical weight) of the lead surrounding that protects the
patient and operator of the xray tube radiation you are considering using.
It doesn't take very many Kv across the tube to make it a radiation hazard.
For example, approax 30 Kvp  (thats Kv peak voltage) is used for mammography
(breast screening), usually considered soft xrays, these lower energy xrays
still pass through a screen (I know of some xray machines that use an
aluminum plate surrounded by lead to form a window) to only allow radiation
to pass through a small window to the desired patient target area.

  The Power supply's are cool, If you have an old one with a standard 60Hz
step up transformer, they make a great Jacobs Ladder if you run them through
a variac first ;-).  Watch out for PCB's on some of the really old machines.
They also have BIG HV sticks and Capacitors.  I'm using the caps out of a
Cockcoft voltage multipier out of a CT scanner as my Primary capacitor (
BTW, still working out the bugs).

Good Luck
Shaun Epp