Re: Who needs a quenching gap ?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Terry Fritz <twftesla-at-uswest-dot-net>

Hi Finn and Gary,

	Finn pretty much tells what he meant below.  The models cannot predict
when a quenching gap will be able to cut off power.  However, if you scope
the waveform, the model can be easily adjusted to match.

	Of course, Finn's gaps, like mine, do not really quench at all.  For years
everyone wanted to find a prefect quenching gap but the materials and
knowledge we have at the moment are just not up to it.  I find that the
gaps I have studied that quench well are just too lossy.  You loose more
making the gaps quench than if you just try to make the losses really low
and let the thing rings as long as it wants.  

	It is possible, once you decide to not quench, to tune the system for a
certain number of nothches which the models can easily predict.  I have not
noticed too much advantage to one, two, or three notches since all the
power seems to go basically to the same places regardless.

Cheers,

	Terry


At 05:11 PM 12/8/2000 +0100, you wrote:
>Gary, all!
>
>I am using the same models, and gap models as you, and maby I am putting
>my opinion incorrectly.
>
>What I mean is, that the model can predict, how many times the energy
>transfers from primary to secondary, back again, and so forth, before
>the energy is completely dissipated into the load. On this coil, it
>happens within 2 envelopes, both in the models as in real life. On the
>Museum coil, the transfer took up to 5 notches, and this was happening
>also both in the model as in real life.
>
>So when I said quench, I really ment energy depletion in the primary
>circuit. And looking a bit more at the coil`s actual behaviour, this
>would be a better description, since the gap actually quenches about
>100µS after breakdown. That is when the cap starts charging again.
>
>Cheers, Finn Hammer 
>
>Tesla list wrote:
>> 
>> Original poster: "Lau, Gary" <Gary.Lau-at-compaq-dot-com>
>> 
>> Hi Finn:
>> 
>> I don't see how any of the simulation models that I'm aware of can predict
>> the quenching of a gap.  The gap models that Terry and I use have a
>> simplistic, predetermined "on" or quench time determined by a one-shot timer
>> (the actual time value is a parameter of that one-shot, you have to
>> double-click on it to see the pulse width or change it).  While the period
>> of the notches is easily simulated and predicted if pri-sec "k" is known,
>> which notch quench actually occurs at on a real gap is a function of gap
>> geometry and other poorly understood factors.
>> 
>> I couldn't see how you achieved the single gap configuration on your RSG.
>> I'm also a firm believer in the loss-benefits of a single gap.  How was that
>> done?  And congratulations on some drop-dead gorgeous construction!
>> 
>> Regards, Gary Lau
>> Waltham, MA USA
>> 
>>  -----Original Message-----
>> From:   Tesla list [mailto:tesla-at-pupman-dot-com]
>> Sent:   Thursday, December 07, 2000 6:23 PM
>> To:     tesla-at-pupman-dot-com
>> Subject:        Who needs a quenching gap ?
>> 
>> Original poster: "Finn Hammer" <f-hammer-at-post5.tele.dk>
>> 
>> Gang!
>> 
>> Today I finally managed to get a scope trace off the new RAT-coil under
>> streamer loading.
>> 
>> This was particularly satisfying, since it confirms the Microsim based
>> preliminary design effort, which predicted a clean 2nd. notch quench.
>> This was recorded at 100BPS, about 1 meter streamer length.
>> 
>> http://home5.inet.tele.dk/f-hammer/ringdown.jpg
>> 
>> Horizontal=50µS/div
>> Vertical:5kV/div
>> 
>> Since the gap is a SRSG with onely one gap in operation, and should
>> therefore be a poor quencher (but possibly a "low losser") this picture
>> tells, that this coil is quenching the gap very well.
>> 
>> I believe it is possible to determine the coubling from this trace, how
>> is that done?
>> 
>> The coil is really just thrown together along the proven R.Quich
>> guidelines 1000 turns, 1:3 dia/length (although it is a fine spacewind
>> on threaded form). So the impedance match btwn streamer and coil is not
>> precise. Zcoil/Zstreamer= 1.6. I have tried to find a way to meet this
>> match, and if anyone is interested, we could talk more about this
>> subject. According to this work, the perfect impedance match is met,
>> when the toroid is arounf 10pF. I can hardly imagine that this would
>> make the coil perform any better than with the present 32pF . I have
>> never managed to create a model of a coil, that quenches at the first
>> notch, so perhaps 2nd. notsh quenching is natural, in some sort of way.
>> 
>> Comments?
>> 
>> Cheers, Finn Hammer
>