From: "hoping" <Hoffmann.Win@t-online.de>
Newsgroups: sci.physics.plasma
Subject: Re: Plasma Quench Technology
Organization: T-Online
References: <87efo5$caq$1@jupiter.cs.uml.edu> <87pv89$iu$1@jupiter.cs.uml.edu>


Hi Walt:

I did this work VERY long ago and to my knowledge nobody has resumed since
then. The idea was to use an effect in analogy to the gasdynamic CO2 laser
principle, which was quite new in those days. (Now you have an impression
how long ago this was!) We (me and my collegues) knew, that very rapid
cooling of a quasi fully ionised plasma in equilibrium leads to
non-equilibrium densities in the excited electronic states of the neutral
atom or molecule, because of the fast recombination of the ion. If
collisional and radiation processes are within certain ranges, even
population inversion should occur. In some cases very high laser power at
comparably short wavelenghts should be possible. This was a result of the
theory. In the beginning it was calculated for hydrogen because it's the
simplest system and the rate coefficients were reatively well known - in
contrast to other gases. Although I knew that the H term scheme was not
necessarily the optimum I spent about two years to try making a high power
CW! hydrogen laser in the near infrared (Paschen). Have you ever seen a deep
blue hydrogen jet? It's a beautiful sight. It was created by supersonic
expansion of an arc discharge in a device originally destined for electric
propulsion in space. It finally turned out, that at electron densities, high
enough to produce a substantial optical gain in the direction perpendicular
to the jet, in contrast to the (simple) theory the cooling was not rapid
enough to produce population inversion at all. Or in other words: The blue
jet with population inversion was too thin. Or the device was too small
respectively. I am quite shure that in the atmospheres of some stars there
may exist sometimes the conditions for a natural laser with only one pass.
The reason for the failure? I still know it not for shure, because my
interest turned to other more short therm promising laser research subjects,
but I think that from the point of view of an electron with high (runaway)
speed, the gas velocity was deep in the subsonic region, so that high energy
electrons could still heat up the plasma all the way down the jet.
Furthermore all the zoo of plasma waves could have had heating capability.
The only way to simply overcome this problem was to leave the idea to
separating plasma production and decay by some distance in space, but to do
just the same thing in time, that means to look in the afterglow of a
decaying pulsed plasma. That's what a lot of people did later with
remarkable results. One of the first was Silvfast at the Bell Labs, and a
lot of work was also done in Russia. Later then the principle was extended
successfully to higher ionised species to obtain UV, XUV and so on.... But I
am still hoping (sic!) that someone will construct the CW plasmadynamic
hydrogen laser. Perhaps you?

Regards Hoping

Hion solar <hionsolar@aol.com> schrieb in im Newsbeitrag:
87pv89$iu$1@jupiter.cs.uml.edu...
>
> Hoping,
> Re: plasmadynamic laser work
>
> Sounds interesting with H2 supersonic jet quenching. Population inversion
to H
> atom [prior to the nozzle or after the nozzle?] but no lasing? How was
the
> laser pumped? Why do you think it didn't lase?
>
> Regards....Walt Pyle
>
>
>
> >Subject: Re: Plasma Quench Technology
> >From: "hoping" Hoffmann.Win@t-online.de
> >Date: 02/04/2000 7:12 AM EST
> >Message-id: <87efo5$caq$1@jupiter.cs.uml.edu>
> >
> >
> >Hi Steve
> >I'm not familiar with the TiCl4 system, but a couple of years ago I did
some
> >work on recombining plasmas with the aim of developing what I called then
a
> >"plasmadynamic laser". The experiments were carried out in a supersonic
> >expanding hydrogen jet. In short, they were not very successful: I
received
> >population inversion in atomic H levels but no lasing. Today I believe to
> >know why. You have to take into account ALL processes, and the problem
is,
> >that you never know all their constants. If you are really interested in
the
> >theoretical background I'll try to find some literature in the
paper-orkus I
> >have here.
> >hoping
> >
> >
>
>
>