[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [TCML] Streamer development recorded with high speed camera
Hi David,
Interesting videos - thanks for sharing them. I suspect there are at
least two effects at work.
First, for streamers that almost or just barely connect, you'll notice
short, seemingly isolated, brighter segments with more diffuse
discharges coming off each end. These brighter regions are called "space
stems" and "space leaders". They appear as sharply defined bright
segments that are actually isolated bright leaders that are supplied bu
current from burst corona coming off each end (negative corona on the
end closest to ground, and positive corona on the end facing the
approaching main negative leader). These are a normal part of the
propagation process for negative leaders (where the HV
terminal/discharge is negative wrt ground).
As the leader propagates, the space leader becomes longer by expanding
in both directions, finally merging with the main leader from the HV
terminal. If the Tesla coil reached its maximum negative potential
before the space leader merged with the main leader, further propagation
stops and we can easily the stranded space leader. Although space
leaders are more readily visible with high speed equipment, they can
also become noticeable with the unaided eye when the spark is nearing
its limit for the applied voltage, or when the capacitance of the
voltage source is comparatively low, limiting follow-through current. A
description of them can be seen here (part of an excellent paper,
"Fundamental Processes in Long Air Gap Discharges" by I. Gallimberti,
et. al.):
http://www.capturedlightning.com/temp/Longgap1_5.pdf
If a leader fully connects, you may see part, or all, of the "return
stroke" as a low impedance path to ground rapidly removes space charge
from the newly connected leader. There is a sudden jump in current at
the far end beginning from ground, and up the channel, making the return
stroke significantly hotter (and brighter) than the previous connecting
leader. Given sufficient time and voltage, the return stroke will flow
all the way back to the topload, forming a bright and evenly lit spark
or arc. However, if the topload voltage just peaked when the final jump
occurred, and the connection is weak, the total leader channel
resistance and declining topload voltage may prevent the return stroke
from progressing very far up the leader channel. In this case, you'll
see localized brightening for only a short distance from the ground
while the rest of the spark retains the dimmer appearance of lower
current air leaders - just the effects seen in the video clip when the
leaders are just barely connecting.
Bert
--
***************************************************
We specialize in UNIQUE items! Coins shrunk by huge
magnetic fields, Lichtenberg Figures (our "Captured
Lightning") and out of print technical Books. Visit
Stoneridge Engineering at http://www.teslamania.com
***************************************************
David Kronstein wrote:
Hey guys,
I took an interesting video today, running my DRSSTC and high speed
camera at the same rate, 120Hz. This allows you to see the development
of the streamers burst by burst.
Youtube video:
http://www.youtube.com/watch?v=nUkeVj8WTQ0
Higher quality AVI:
http://4hv.org/e107_files/public/1235979158_347_FT0_tesla.avi
It takes a few pulses to grow the streamer enough to make contact with
the duct on the left (~1m distance). I also notice a brighter, frantic
arc action near the duct. I've seen this brighter section near the end
on Van de Graaff sparks too. Any idea what causes it?
David
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla