Technical factoid

[ffutures]

Someone, somewhere probably needs this information - I have no idea who though...

Everything I've read about helium-neon lasers says that the tubes invariably leak and only last a few years. But I've just noticed that the one we have at work (Uniphase 4mw, originally intended for a medical sensing application) was made in May 1990. We don't use it much, since we're not supposed to use anything above 1mw without a lot of extra safety precautions, but it's still working.

I don't know how this scales up to more powerful lasers, lasers that are in full time use, etc., but it surprised me.

Comments

[nelc.livejournal.com]

I suppose that if it doesn't get used much, then it doesn't get warm often; warm helium will leak better than room-temperature helium? Or you could just have one that was better made than the others.

[ffutures.livejournal.com]

Could be that, could be you lose more when it's in use and ionized. Not sure temperature is much of a factor, it doesn't seem to get particularly warm - but again a more powerful one might.

[dsample.livejournal.com]

Given that helium and neon have the two smallest molecular sizes of all substances, they will leak out of containers that can hold *any* other substance.

I suppose that it's possible that every once in a while the vessel that holds them in the laser will be so perfectly sealed that they won't leak, but I suspect that it's more a matter of luck, than anything else.

[ffutures.livejournal.com]

Exactly - and it occurs to me that I have no way to measure its power, it's still working but for all I know it's lost some gas and is down to a milliwatt or two now.