Full Version: Laser tube life

From: Harvey only (HARVEY-ONLY) [#1]
 27 Feb 2007
To: ALL

I learned something at the Vegas show. Why some laser tubes fail from sitting around and others do not. This is aside from electronics failure from moisture.

One of the gasses in the CO2 laser mix is Helium. While the Helium molecule is larger than Hydrogen, it is the second smallest gas molecule that there is. If the tube seal is not absolutely perfect the Helium can escape slowly rendering the tube useless.

(The Hydrogen molecule can escape through solid steel it is so small.)

From: Dave Jones (DAVERJ) [#2]
 27 Feb 2007
To: Harvey only (HARVEY-ONLY) [#1] 27 Feb 2007

OK, but why is it that the tube that sits unused will leak the helium, while one that is used for say 10 minutes a week won't?

From: Harvey only (HARVEY-ONLY) [#3]
 27 Feb 2007
To: Dave Jones (DAVERJ) [#2] 27 Feb 2007

The tube in use probably will leak faintly more due to temperature. (Or maybe faintly less due to a more active molecule vibrating more due to temperature. I really do not know.) [Too much education gets confusing.]

It basically tells us why there is a shelf life on some tubes.

Either you get lucky or you don't.

From: JHayes55 [#4]
 27 Feb 2007
To: Harvey only (HARVEY-ONLY) [#3] 27 Feb 2007

quote:
I really do not know


If you did know what would be your answer?

From: Harvey only (HARVEY-ONLY) [#5]
 27 Feb 2007
To: JHayes55 [#4] 27 Feb 2007

Probably one or the other.

From: UncleSteve [#6]
 27 Feb 2007
To: Harvey only (HARVEY-ONLY) [#5] 28 Feb 2007

"When you come to a fork in the road, take it", Yogi Berra

From: Stunt Engraver (DGL) [#7]
 27 Feb 2007
To: UncleSteve [#6] 28 Feb 2007

Steve,

The story behind that quote, which is often evoked at graduations, is that Yogi was giving directions to his home and there was only one way to turn at that intersection.

It's since turned into something much more profound. :-)

From: jeanettebrewer (JEANETTEBREWER2) [#8]
 28 Feb 2007
To: JHayes55 [#4] 28 Feb 2007

quote:
If you did know what would be your answer?


Joe,


You're a quick learner! You'll have that well-deserved CRS designation in no time!

From: Harvey only (HARVEY-ONLY) [#9]
 28 Feb 2007
To: JHayes55 [#8] 28 Feb 2007

And a good sense of humor including jumping threads.

From: JHayes55 [#10]
 28 Feb 2007
To: Harvey only (HARVEY-ONLY) [#9] 1 Mar 2007

Harvey my friend - I always learn quickly when listening to smart people like
you and I was testing your theory - but your too quick for me. No surprise that Jeanette got it though - it's like she has radar.

The package of items you emailed me were great - have not had a minute to play with them yet but I will.

From: Doc (GREAT_ATLANTIC) [#11]
 1 Mar 2007
To: Dave Jones (DAVERJ) [#2] 1 Mar 2007

quote:
OK, but why is it that the tube that sits unused will leak the helium, while one that is used for say 10 minutes a week won't?


I've been told that the heat generated by just a small amount of use each day/week is enough to keep the gaskets supple and seated properly. When left cold for long periods, the material in the gaskets can harden to a point where micro-fractures allow the gas to escape very slowly.

From: Dave Jones (DAVERJ) [#12]
 1 Mar 2007
To: Doc (GREAT_ATLANTIC) [#11] 1 Mar 2007

That seems reasonable. Thanks.

From: Harvey only (HARVEY-ONLY) [#13]
 1 Mar 2007
To: Doc (GREAT_ATLANTIC) [#11] 1 Mar 2007

Bits and pieces of information from here and there do start to form an answer.

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