Re: Laser Triggered Spark Gap

To: tesla-at-pupman-dot-com
Subject: Re: Laser Triggered Spark Gap
From: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
Date: Tue, 03 Nov 1998 18:55:59 -0700
Approved: terryf-at-verinet-dot-com
Hi Steve,

> Original Poster: "Steve Young" <youngs-at-konnections-dot-com> 
> 
> To fellow sparkers,
> 
> This list has a lot of discussion about spark gap performance, quenching,
> etc., which certainly is valuable and needed.  For static gaps, discussions
> seem to indicate quenching is improved for wider gaps.  But a point is
> reached where the gap is too wide for spark initiation.  Thus the need for
> a means to "help" a wider gap initiate a spark.
> 
> Occasionally the use of triggered spark gaps is mentioned, but the thread
> soon dies.  I would think this is an area for experimentation which could
> yield a LOT of benefits.  For one thing, the bps could be under our precise
> control simply by varying the trigger frequency.  If one chose to lock the
> trigger frequency to the AC line frequency and adjust the phase
> relationship, one would in effect be able to duplicate the performance of a
> RSG without having to mess with high RPM balanced rotors, etc.  Having the
> gap fire when WE want it to instead of when it can no longer resist firing
> itself would make for much better control and scope pictures for some of
> the other testing Terry and others are doing. 

A longer gap is going to increase gap loss somewhat (and probably 
improve quench in the same breath). 

> The various triggering mechanisms have been touched on in this list.  These
> can range from pulse generator driven ignition coils to lasers.  My
> experiments with SCR driven crummy ignition coils indicates they are good
> for break rates up to at least 800 bps.  I don't know how the good GM
> ignition coils perform at higher break rates - anyone have some experience?
>  
> 
> Lasers would have the advantage of being able to simultaneously trigger a
> bunch of aligned series gaps by aiming the beam through all the gaps.  I
> suspect some Marx generators are fired that way.  But where can the
> cash-strapped experimenter find a suitable laser which can sufficiently
> ionize the air to initiate spark breakdown?  The only potential cheap
> sources I am aware of would be to use a $15 laser pointer in a pulse mode. 
> Would this work?  Specifically, can the laser diodes handle microsecond
> pulses of a much higher energy without self destructing?  If so, could they
> produce enough pulse energy to trigger spark gaps?  If so, what would the
> pulse width and peak power need to be?  Does anyone know what the laser
> diodes used for tattoo removal, etc. cost and where to get them?

You cannot overload laser diodes more than once. The mirrors get 
destroyed.
 
> In summary, isn't it time to move toward triggered spark gaps for
> disruptive TCs?

Agree. Been lazily thinking about this for some time. My approach 
would be something like an open air flashtube - fairly large diameter
pyrex pipe with a trigger electrode placed around it. I haven't tried 
it yet though.

Malcolm