video....

To: mail11: ;
Subject: video....
From: pierson-at-msd26.enet.dec-dot-com
Date: Tue, 19 Nov 96 15:55:50 EST
Cc: pierson-at-msd26.enet.dec-dot-com
>I was reviewing some frame by frame video hits of maggey #11-E and note 
>that the arc channel develops over an extended period of time!
	'sfunny.  I was just wondering if anyone had done studies like this.

>I note a spark approaching the heavily grounded aluminum siding on my 
>house.  The contact occurrs, let us say, at t0, in frame, f0.  The arc 
>channel is fairly dim, but contact is made and the arc channel is 115" 
>long point to point.  In the next frame, f1, (1/30 second later) the 
>channel doubles in brightness.(as measured by my light meter (spot 
>reading).  In frame f2 the arc channel increases in brightness by another 
>40% or so over the preceeding frame.  In frame f3, the channel retains 
>about the same brilliance (white hot) as in f2 frame.  In frame f4, the 
>channel starts to reduce its brightness and is about 65% of f2s level.  
	caveat;
	the video system is subject to 'light' and 'electronic'
	saturation.  energy might be changing, but not captured, if the
	cell (or the electronics) was already at 'max white'.  light meter
	measuresa re admirable.  might be instructive to try again, similar
	setup, with neutral density filters to attenuate the light.

>Frame f5 shows a greatly reduced channel intensity and is just about 10% 
>below that of f0s level.  In frame f5, The channel is just a faint mist 
>of ionized vapor.  Frame f6, shows the channel to have disappeared.
	LOTS of what is going on is way to fast for the eye to see.  My
	personal ASSumption has been that any given 'spark' was restrikes down
	the same channel, as with lightning.  Does the cam have faster
	'shutter speed', or slow motion (high frame rate)?  Each, if available,
	might add to the information.

>Assuming 400 BPS (which is my normal break rate), This means that the 
>system has energy pops at the rate of about 13 pulses per video frame. so 
>we see that from time of contact to max brighness,(more or less), we 
>actually sent in about 52 energy pulses.  Is the electronic Q of the 
>resonator system this slow to respond?!!  Energy delivery to the arc 
>channel was consistently on the increase over this long period 
>(~120,000 usec).
	This is a good question, and affects system set up:
		for sparks (one case) or for max_but_no_sparks, another case.

>The rise to max channel current is rather slow, compared to the 
>extinguishing of the channel which never takes more than 2 video frames 
>(1/15 sec-60,000usec).
	And why does it extinguish?

	all i can guess is that each 'energy' pulse takes more and more from
	the primary storage (tank storage) until insufficient remains to
	maintain the spark channel.

	regards
	dwp