Quench, Coherence etc.
From: Gary Lau 11-Aug-1998 1508 [SMTP:lau-at-hdecad.ENET.dec-dot-com]
Sent: Tuesday, August 11, 1998 2:26 PM
Subject: Re. Quench, Coherence etc.
>From: Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
> Here are a few results obtained from some experiments. Power
> supply was DC charger, BPS = 1.
> Two Coil System
> Lsec : 20.6mH, Csec : 13.5pF, H/D : 4.8, Cterm : 6pF or so
> Fs(w. term) : 250kHz
> Lp : 17uH, Cp : 25nF, Vp : 13kV (system breakout about 9kV)
> Ep : 2.1J
> Ttransfer : 12uS, Ringup : 3 cycles of Fs, k : 0.16
> Gap = adjustable pipe gap. Number of gaps varied from 2 to 8 during
> tests. Adjusted to fire at 13kV for each number of gaps.
> Results: - 2 gaps : no effective quench except with attached streamer.
> Mostly 3, 4th notch quench. 11" hot blue spark to ground
> rod 20% of the time.
> - 4 gaps : quench mostly 2nd notch w. no breakout, always
> with breakout. Spark about the same as 2 gaps.
> - 6 gaps : quench always 2nd notch. Spark increased to 11.5"
> 20% of the time.
> - 8 gaps : quench always 1st notch. Spark 10.5" for 20% of
> shots - yep, it decreased.
>***** I looked in vain for any signs of a shift in V/I distribution
>in all tests, breakout or not. Coherence if it exists remains
>elusive. The resonator was carefully chosen to have a delay line type
>H/D with only a 1/4 of the total capacitance in the top. I
>superimposed the beat envelope captured in the scope on the first
>notch quenched waveform.
> If breakout did not occur under optimal quench, the secondary
>oscillated to no good effect for a very long time but it was all
>decay after quench. No sudden rise in amplitude; in fact no rise at
> A most interesting thing was noted that suggests that optimum
>quench <> optimum sparks (also suggested in the spark lengths above).
>For the same breakout conditions, the amplitude of the waveform was
>significantly higher in the second ringup than if the system
>optimally quenched and decayed. In effect, the coil had two hits at
>the air some time apart and with still high amplitude on the second
>hit. Arc dynamic theorists might have something to say about that one.
> I made a note elsewhere about the streamers observed and how
>their number related to breakout voltage and ROC.
>Sorry about the unintended snippage.
What I read from this experiment was that as the number of gaps increased,
the quenching improved, but that spark output diminished as gaps increased
above a certain point.
Terry Fritz's experiments comparing multi and single gaps at various coupling
coefficients also showed that with single gaps, higher secondary currents
resulted, but at the expense of inferior quenching.
This appears to suggest higher gap losses in multi-gap designs. That Terry's
multi-gaps quenched better than his single gap is not surprising since
neither of his gaps had any sort of forced air flow. Could a "full
blown" single gap with optimally adjusted airflow offer better performance
(not necessarilly better quenching) than a multi-gap arrangement? I'm nearing
completion of such a gap and will report on it's comparative performance soon.
Regards, Gary Lau
Waltham, MA USA