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Q & A: running gas lasers

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Most recent answer: 10/22/2007
Q:
Hi,

I have a bunch of lasers and the manuals all say that the tubes will last longer if they are run a few hours a month.

I used to work in an analytical chemistry lab and the chemist said that the gas filled tubes for the Atomic Absorption machine went bad if they weren’t run all the time. However, I pulled out a hollow cathode tube that looked like it had never been used but was in a box that looked 30 or 40 years old and it was very strong.

What is the physical reason for saying that gas filled tubes last longer if they are run "A few hours a month"?

I have a degree in physics and have asked a number of PhD phycists and chemists this question and have not received even an attempt at an answer.

Thanks, j.
- j. robert dobbson
Kentfield, CA, USA
A:
When I used to use an argon ion laser we found that the conventional wisdom that they should be run fairly often seemed to be correct. The reason we heard is that impurities gradually leak out from the glass into the gas. The impurities interfere with the lasing. These impurities are swept out by the electrical current (getting trapped on the electrodes or somewhere) when the laser is running. If you let their concentration drift up too much, the laser won't even start up.

Mike W.

Lee H

(published on 10/22/2007)

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