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From: siegman@sierra.Stanford.EDU (Anthony E. Siegman)
Newsgroups: sci.electronics
Subject: Re: LASER info needed
Message-ID: <532@sierra.stanford.edu>
Date: 28 Feb 90 00:10:48 GMT
References: <44900003@uxa.cso.uiuc.edu> <2232@rodan.acs.syr.edu>
Sender: siegman@sierra.Stanford.EDU (Anthony E. Siegman)
Reply-To: siegman@sierra.UUCP (Anthony E. Siegman)
Organization: Stanford University
Lines: 36


>1. You have a high power laser cutting machine.  It is used for cutting
>    up to 1/2" thick plates of metals (steel, alum,...) into rough cut


>3. How would & what is the best way/method of containing the laser beam, after
>   it penatrates the material, OR if the beam is running & there isn't any 
>   material to penatrate.

If you are talking about a real system here, the laser is almost
certainly a CO2 laser with a wavelength near 10 microns in the middle
infrared, and the cw power output level from the laser is somewhere
between 300 Watts and 3 kilowatts CW.  This is not too horrendous a
machine, because the efficiency of CO2 lasers from electrical power
supply input to laser beam output is at least 10%, and might be a
factor of two or three better than this.  Such a laser might cost a
few hundred thousand dollars, including power supply, controls, and
some of the material handling equipment -- in other words, comparable
to what a high-performance machine tool of any other kind costs.

As to what you do with the beam when you're not cutting with it?
(besides just turn the laser off).  Well, laser beam like this focused
into a tiny spot with a lens will do horrendous cutting, melting,
vaporizing of the material in that small spot (analogous to but
considerably more powerful than the heating effects you can do when
you focus sunlight with a small hand lens) But suppose you let the
beam expand back up again to, say, several inches in diameter and then
catch it inside a heavy metal can, perhaps lined with carbon black,
and cooled with flowing water.  OK -- you are putting somewhere
between a few hundred watts and a few kilowatts of power into that
"beam catcher" -- no worse than if you had somewhere between 3 and 30
hnundred-watt light bulbs inside the can and were trying to carry away
the heat.  A little water cooling will do it.  Also, you probably
bounce the beam around inside the can, letting it hit various cooling
fins, so that the heat gets absorbed over a large surface area instead
of being focused into one spot.