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critical damping of spark discharge




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From:  Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
Sent:  Saturday, June 06, 1998 7:43 AM
To:  Tesla List
Subject:  Re: critical damping of spark discharge

Tesla List wrote:
> 
> ----------
> From:  Jim Lux [SMTP:jimlux-at-earthlink-dot-net]
> Sent:  Friday, June 05, 1998 7:05 PM
> To:  tesla-at-pupman-dot-com
> Subject:  critical damping of spark discharge
> 
> I have discovered that the EG&G application note talking about
> critically damped RLC circuits with a spark gap is now available on the
> web:
> 
> http://www.egginc-dot-com/bin/webmate/Opto|111/page/egg/1300tb1
> 
> Now, this talks about the stuff for flash tubes, however, by suitable
> (?!) adjustment of the Ko parameter in the Goncz equation, it should
> work for an air spark gap.

Jim and all, 

The difference between the flashtube and a free-air arc is that the cool
sidewalls of the flashtube actively cool the arc plasma. This additional
boundary condition results in a positive ("resistive") VI curve once the
arc current exceeds a critical level. 

An arc in free air can expand with increasing current density, resulting
in a negative VI characteristic for lower arc currents (10's of amps),
and a virtually flat, zener-like clamped voltage VI characteristic for
higher currents. At very high currents there's a very weakly positive VI
characteristic primarily due to electrode resistance effects. 

The flashtube and free-air cases are unfortunately not comparable...

-- Bert --