Optimal CO2 laser temperature?

[Things]

So, now that my laser cutter is up and running, I've started to notice the effect of water temperature on laser output. More specifically, at one stage the water loop developed a leak, and the laser was running very warm, and the power drop was quite significant.

I haven't really been able to find what the optimal operating temp range for a sealed CO2 laser is?

I have a 240mm radiator in the cooling loop, however if it prefers running at lower temps (Say, below 30C ish), I do have a water chiller I could adapt. My question is, would using the chiller be worth it in terms of either lifetime, beam specs or output power?

Cheers,
Dan

[macona]

Chinese tube?

We had a 80 watt chinese machine and I think the chiller was set to somewhere around 15c.

[ionlaser555]

I've herd That around 15 to 20 , maybe to 25 C is ok , one thing with co2 tubes is as the temprature goes up power can drop rather steeply .

[macona]

I think anything at room temp or lower is fine. My guess temp rise increases tube pressure enough to change the discharge characteristics.

[Things]

Problem is, where I live, room temp is basically always over 30C, sometimes probably more like 40C then add the laser temp rise. I think I'm going to have to use my little chiller, or find another one to put in series with it for more cooling capacity. I found the other day my laser was being way overdriven, so my little chiller might have a hope of keeping up with it yet.

[macona]

It is pretty easy to overdrive the chinese tubes. The software is never set so that the max power setting is the tube limit. They just run the PWM 100% which is usually too much for the tube.

[Things]

Yeah, I've built this entire unit myself, but only bothered getting a current meter the other day. Was shocked to find out it was being driven at around 29ma, which is insane!

Dropped it to a much more reasonable max of around 14mA. I'm assuming I didn't actually get any performance increase from the huge overdriving, just increased heat output and a few hours off my tube life.

[ionlaser555]

Good to see its going ok again , Wow that is abit over the normal current .

One reason temprature rise affets power so much is , as the tube heats up less energy is removed from the helium atoms , thus the nitrogen carnt give the left over energy they have from giving it to the co2 atoms , to the helium . So the nitrogen carnt drop to normal energy state and start over by getting exscited by the HV discharge . the hotter the tube the less the process happens thus power drops right off :P .

[Things]

Just tried again with the tube current limited to 18mA, and I seem to have gained a little more power. Before I needed 2mm/s at 100% power to cut through 5mm acrylic reliably, now at 2mm/s and 100% power it cuts thru fast enough to roast the MDF bed I have underneath. Still, not a huge increase, but I'm probably expecting too much from a 40W laser.