Re: lasers to generate plasma in atmosphere


"zashi" <tragic.descent@xxxxxxxxx> wrote in message
news:dd99f5a2-4a26-43b5-888b-1556965dc1f4@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
| I'm wondering what kind of laser, I'm guessing something between
| ultraviolet and X-ray, and how much power would it take to create a
| thin beam (a few mm) of plasma in atmosphere from the laser source to
| 50+ meters away? If the distance is too far, then how about for 1m?
|
| I'd be happy with a few equations to answer my questions. Google
| search, for once, doesn't seem to even come close to an answer for
| this.

The first part of your question, "what kind of laser?", is best answered
by "what kind of plasma?"

http://en.wikipedia.org/wiki/Plasma_(physics)


The second part, "in atmosphere" can only refer to a mix of nitrogen,
oxygen, carbon dioxide, water vapour and a trace of methane from
swamps and cattle farts. A plasma is a hot substance with electrons
stripped away, but it still a particular element.
The third part, you seem to think that the gas will be ionized along
the entire length -- in reality atoms that absorb part of the beam close
to the source will shield the atoms further away and so the power
needed will be proportional to the distance - and you've given a
range of 50 metres to one metre.
The fourth part, "a thin beam of a few mm" is a pretty fat beam
when you consider the size of a DVD/CD writer with gigabits of
information stored (and read) by a very small beam indeed, much
thinner than the point of a needle.

--
Why did Einstein say
the speed of light from A to B is c-v,
the speed of light from B to A is c+v,
the "time" each way is the same?

1/2[tau(A)+tau(A')]= tau(B)
where
A = (0,0,0,t)
A' =(0,0,0,t+x'/(c-v) +x'/(c+v))
B = (x',0,0,t+x'/(c-v))
x' = x-vt

Ref: http://www.fourmilab.ch/etexts/einstein/specrel/www/figures/img22.gif

"Easy: he did NOT say that." - cretin harald.vanlintelButNotThis@xxxxxxx
According to moron van lintel, Einstein did not write the equation he wrote.
Androcles



.

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