I have the laser up and running with the 100 watt tube and it is indeed VERY controllable right down to %4 of rated power.
I can engrave on paper without cutting through at speeds of 100mm/s and then cut right through pine wood 18 mm thick in a single pass. Probably more if I had a more powerful air pump. I have set my MAX power setting to 90% in software so I don't run it too hot. I will also need a chiller as the little air radiator I have just isn't enough to keep up the cooling with cutting 600 snow flakes 8" in size. I ended up getting another bottle of distilled water and putting it in the freezer for a few hours and then alternating the bottles to keep the water temp under 24 deg. pretty hard when the ambient is 43 deg in the shed.
The only thing I am really worried about is having it in the shed when the temp get to below freezing and the water in the tube freezes and wants to crack the glass. I hope this doesn't happen but it is something I can live without.
Time will tell if the tube is good value for money. So far I am VERY pleased with it.
The tube hasn't got a metal to glass seal and upon further inspection it has the ends glued on like all the rest but I don't know if there is an o-ring seal in there or not. The glue seal is very thin and hard to detect except if you look closely.
Rich.
I am not completely useless.......I can always serve as a BAD example.