TSSP: List Archives

From: "Malcolm Watts"
Date: Tue, 3 Jul 2001 08:42:31 +1200
Subject: Re: [TSSP] Toroid breakdown voltage indirect meas.

Hi Paul,

On 2 Jul 01, at 11:59, Paul wrote:

> So we have observations of a blue/violet 'cloud', diffuse, very faint,
> 
> Malcolm wrote:
> > ...on closer examination looks like faint streamers emitted in all
> > directions
> 
> but of the same order of radius as the eventual streamer length,
> occuring
> at a  voltage distinctly lower than that at which obvious streamers
> appear.
> 
> If we can observe this effect and at the same time apply a direct top-
> volts measurement, we can try to relate it to the toroid surface field
> strength.

I've decided to set up a coil this coming Sunday to see this again. I 
will make the pertinent observations and answer the other questions 
below.
 
> We do have a problem already with this surface field issue, in that
> Thor does not break out at the point we think it should - at a Vpri of
> 14.7kV.  We can surely trust the Vtop estimates based on this, since 
> Thor remains below breakout and there is no significant corona. We may
> have to look at the field calculations again and try to cross check 
> them, but this is a clear and large discrepancy even without a direct 
> Vtop measurement.
> 
> Malcolm wrote:
> > It is very close to what one would consider to be the breakout
> > threshold. 
> 
> Are we talking just a few percent below the the breakout volts, or as
> much as 10 or so percent? 
> 
> Of course, it would be very nice if Marco reports observation of this
> faint aurora at say 16 kV.
> 
> Does anyone know anything about photo-ionisation?  UV photons emitted by
> relaxing ions in the streamer passing some distance through the air to
> ionise an atom some way away, thus seeding a new electron avalanche from
> that point?  Does this phenomena play a role in TC discharges?

I've seen daylight affecting the striking voltage of neon lamps. I 
wouldn't know how such an effect affects TC operation.

Regards,
malcolm


Maintainer Paul Nicholson, paul@abelian.demon.co.uk.