Re: Research on lasers + high voltage discharges

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

Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net> 

At 07:48 AM 10/14/2004 -0600, you wrote:
>Original poster: Teslamad-at-aol-dot-com
>Did anyone read that post that just went out about that new research on 
>using lasers to direct high voltage discharges? It looks like one of the 
>many dreams of tesla! HA HA "Death ray" If you haven't, you should check 
>out the power point presentation they have at their site. I sure hope the 
>person that sent the idea to the list is reading this because I lost the 
>E-mail including the links etc. Please send it again. PLEASE. It was real 
>intriguing! Imagine, being able to direct (assuming I understood the 
>research correctly) a high voltage discharge with a laser beam. Does 
>anyone know how this is even possible??? How can a laser which emits 
>photons (a mass less particle... emphasis) direct a flow of plasma? If 
>anyone does get a chance to see this again, take a look at the car test. 
>Its amazing! They shot the laser over the car, sent a discharge along the 
>beam, then cut the laser and naturally, the plasma found its way to the 
>hood of the car! Someone please respond to this, and please resubmit the 
>link if the original sender is reading this!
>
>Thanks again
>
>Regards,
>~Drew

It's not so far fetched as you might imagine. The Japanese have been doing 
work with high power lasers for lightning protection.  Since the 1970's 
lasers with enough power to breakdown the air along the beam have been 
available.  Once you've got the breakdown, the air is ionized (plasma), and 
low resistance, so the electrical discharge will follow it.  The real trick 
would be in creating the breakdown "somewhere else" other than along the 
beam axis.  I think the Japanese researchers were using multiple beams, 
each of which, individually, wouldn't have enough field to reach breakdown, 
but when combined at an intersecting point it would cause a breakdown.

The breakdown occurs very fast, so you can use a rapidly pulsed laser, with 
very high peak power short pulses, but with lower average power.  It's the 
peak power that causes the breakdown by exceeding the 30kV/cm breakdown 
threshold, not the joule heating.

if you want to calculate it.. Power density (watts/sq meter) = Efield 
(volts/meter)^2/377

Substituting in 3MV/m for air.. 3E6^2/377 = 24GW/sq meter....

Sounds like a lot, but consider that if you focussed a 100 W CO2 laser down 
to a 0.1mm spot (10 wavelength in diameter... not too challenging), you'd 
be at 13 GW/sq m.

There are lots of MW peak power lasers around with short (few nSec) pulses.


There are also some really, really big lasers that have been built for 
missile defense kinds of applications.  Take a look at things like 
MIRACL.  These are often gasdynamic lasers which a laser scientist I know 
calls: Rocket engines with mirrors.