Re: First THOR measurement results

["Finn Hammer" <f-hammer-at-xxxxxxxxxxxxx> (by way of Terry Fritz <twftesla-at-xxxxxxxxxx>)]

Tesla list wrote:
> 
> Original poster: "Marco Denicolai" <Marco.Denicolai-at-tellabs.fi>
> 
> Hello everybody.
> 
snip
> 
> Question 1
> ---------------
> You can see in my web page (first 3 shots) the primary voltage when
> breaking out
> into air, to ground or with no streamers.
> 1. Discharging to ground sucks quickly all the energy away. That's OK.
> 2. To discharge into air, I needed to add a copper stick on the top of the
> toroid: only then I had a secure discharge into air or to a nearby grounded
> rod.
> Breaking into air sucks pretty quickly too all the energy away and there is
> also
> nothing strange with that.
> 3. With no copper stick I have difficulties to get any streamer at all. This
> makes me think that I don't generate enough potential at the secondary to
> breakout. The toroid r.o.c. is a little too big. But my RSG is unable to
> quench!!! See the snapshot!



Sticking a rod out into the air is a rather crude way of insuring that
breakout will occour, however effective.

A method that allows you to fine tune the breakoutability of your toroid
follows: Take a 1 cm square of alluminium tape, and stick it to the
toroid, leaving a small snip of the one corner protruding. A streamer
will issue from this point easily. The drill then is, to progressively
smooth down this small piese of tape, untill you reach the highest
voltage level, and still get breakout. Don`t worry about the toroid ROC
being too big, it will allow you to store enough charge for great
streamers, triggered at the voltage level determined by the protrusion
of the tape bit.
On my Museum coil, which is running at about the same power level as
your current setup, the toroid is 12" (300mm) ROC and I have only rarely
had the guts to provoke breakout from the bare toroid itself.


> 
> Question:
> - do you agree with me about the above?
> - I think that if I could quench the RSG I could accumulate more charge
on the
> toroid, reach the actual breakout threshold and get longer streamers WITHOUT
> NEEDING THE ROD: do you agree?
> - in order to better the quenching, shouldn't I add a fixed SG set in
series to
> the RSG? Wouldn't that be OK?


Perhaps, although I fail to see, how you can ever get higher voltages
than that acheived at the 3 cycle of the first beat. A static gap can
only add more losses, and reduce this voltage, so as far as I see it, it
would be better to adjust the breakout voltage of the toroid as
described above.


> 
> Question 2
> ---------------
> The performance of Thor (spark length) decreases quite rapidly within 15-30
> seconds. This is expecially noticeable without the copper rod placed on the
> toroid: then streamers are quite rare and stop coming within 10-15 seconds.
> What
> might be the reason? I suppose the RSG overheating and crippling the
quenching
> or what? I have already heard of this kind of behaviour but I can't
recall what
> was the explanation. Anybody?


Are there any sharp edges on the electrodes? I would round the
electrodes into a (at least) semi hemisphere to obtain: 
1) Greater voltage hold off properties, leading to a shorter, less
powerconsuming arc.
2) Greatly reduce the possibility of local hot spots, and edge corona.

Cheers, Finn Hammer