From: Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Sunday, August 03, 1997 4:54 PM
Subject: Coiling Waveforms.
Well I did get around to some coiling last night. I
scoped waveforms off the running minicoil using a storage
oscilloscope. I have taken photographs of these waveforms and will
forward them along with lighted photos of the twins to TCBOR (Richard
Hull) who have kindly agreed to be a distribution centre for a modest
cost recovery fee. Should be interesting to those without
oscilloscopes to see exactly what goes on in a typical running TC.
Some points of note:
- optimal 1st notch quenching always occurs for the longest attached
single channel streamers the system produces, either as a single or
- The mica caps are excellent from the low loss point of view. I
captured an excellent waveform of no breakout conditions showing
multiple beat envelopes (5 - 6) with the _linear_ primary decrement
clearly impressed on the secondary waveform until quenchtime. Gap
losses are clearly the dominant force in an otherwise good primary.
- There was absolutely _NO_ difference between secondary waveforms
captured at 1 BPS and 300+ BPS under identical loading conditions.
In fact, there was so much quiet time between gap fires at 300 BPS
that expanding the captured waveform out from 1 mS/div to 5uS/div
showed no clear secondary ring at all (was beyond the y storage
resolution). Yet, the sparks were there alright :)
- To see the rings etc required high speed timebase settings (e.g. 5
and 10 uS.div). I would like to say right here: if you believe that
the secondary gets rung up and up with successive primary shots at
300 BPS, you are wrong! The gap fires showed up as mere blips on a
straight line. Still the sparks wax and wane and grow and die. This
is undoubtably an ionic storage/persistence effect.
- Because of the low power involved (33W) I was obviously able to get
quite close to the system. I took a photo showing the scope just a
couple of feet away from the coil/s which is where it stayed during
the measurements. Of real interest was the fact that after a few
seconds repetitive running, my sweatshirt started clinging to my
chest. ES at work :)