Slow Wave Helical Resonator Experiment

Hi All,

	This is an old subject but tonight I repeated an experiment described in
the paper "Tesla Coils: 1890-1990  100 Years of Cavity Resonator
Development" by James and Kenneth Corum.  In that paper, they describe a
phenomena where the voltage on the secondary rises by standing waves in the
secondary after the primary spark goes out.  They describe how the Tesla
coil behaves as a "velocity inhibited quarter wave resonator".  In this
paper they describe the secondary voltage increasing to very high values
after the primary spark has gone out.   Apparently over 10 times what it
was during the ring-up period.  Those that have studied their paper will
recognize this as being the subjects of Figures 4 and 5 in that paper.
They also describe the "coherence time" as the time it takes for this
voltage rise to reach a maximum.  This is under low loss or no breakout



are the scope waveforms that show secondary terminal voltage (top trace
200kV/div) and primary current (bottom trace 100A/div) that I measured
while repeating their described experiment on my system. This was with no
breakout on the terminal.  The coherence time they describe should be 114us.  

	As the scope picture I posted shows, there was absolutely no observed
voltage rise. The primary circuit quenching is clearly defined in the
bottom trace occurring at 180uS (50us/div) on the fourth notch after the
initial burst began. The secondary voltage at 294uS (180+114) appears very
stable at ~70kV peak with no voltage rise or any evidence of the effects
described in the Corum's paper.

	Many have questioned this part of the paper.  No one has been able to
reproduce the results or claims this paper makes.  There are obvious
theoretical and conservation of energy issues with this phenomenon as well
which tend to conflict with the paper's claims.  Many people have failed to
reproduce this and I now add myself to this list.  This paper was written
in 1990 and we obviously know much more now than was known then.  There is
probably no value in rehashing this subject too much but I had the
equipment setup and I was curious to find the answer for myself as well... 

	Terry Fritz