Re: Measuring Streamer characteristics

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

Original poster: "Bob (R.A.) Jones" <a1accounting-at-bellsouth-dot-net> 

Hi all,


 >Subject: Re: Measuring Streamer characteristics
 > Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>
 >
 > Hi Bob,
 >
 > Greg measured the streamer current for the Electrum directly from inside
 > the sphere (he was INSIDE it while it was running!) with a hand held
 > scope.  I have a top load sphere with fiber probes built into it.  This is
 > how we came up with the 220K +1pF per foot of capacitance model for a
 > streamer load.
 >
 > http://hot-streamer-dot-com/TeslaCoils/MyPapers/modact/modact.html
 >
 > http://hot-streamer-dot-com/TeslaCoils/MyPapers/smallar/smallar4.html
 >
 > http://www.lod-dot-org/electrum/electrumspecs.html
 >
 > http://www.lod-dot-org/electrum/electrumfull.jpg
 >

Nice work Terry and Greg very interesting.

I notice from both streamer current profiles there is an initial triangle
pulse of current approximately at the peak positive top load voltage.
The pulse has a duration of about 5us I assume this is the initial break
out. Given the different sizes of the two system the pulses are very
similar.

In the case of  Electrum there are then three bursts of oscillation at
alternate voltage minima of the top load while the current builds to an in
phase value with the top load current.
Which means its 90deg out of phase with the top load voltage.!!! I suspect
the burst of oscillation is when the streamer connects to ground but then
why the difference in top load current and streamer current.?????

In the case of Terry's papers the second one seems to support the
oscillation idea when the streamer connects to ground.

Assuming the first paper is a streamer to air, in one cycle the streamer
current develops in to an in phase (aprox) current with top load voltage.
A visual estimate of the predominantly resistive impedance is 240kV/0.8A =
300k . The streamers were believed to be between 12 and 24 inches long.
Of cause  a better value could be obtained from processing the data points.

Unfortunately we don't know if the streamer was growing during the
successive current cycles. Its length may have formed in the first current
pulse.

Some cams have exposures times of a 1us and many have 10us.  Unfortunately
most don't have a sync input.
Even with minimum exposure times of 100us provided you could sync the start
of the exposure to a particular peak of the output voltage and the was some
repeatability form streamer to streamer it should be possible to determine
of the there is significant streamer growth during repeated cycles.
Assuming no sync is available perhaps a bar graph display could be
synchronized to the coil and just take video at the shortest exposure with
the bar in view with the streamer.  Occasionally the start of exposure could
occur on a particular cycle of interest. Probably a very tedious experiment.
Perhaps the coil could be synced to the cam. This could be very simple for
those with the right kind of coil.

Thinking about the above presumably the guys with variable burst width SSTCs
can answer that if they have not done so already.


Bob