I'm trying to decide on how to monitor the tube temp, i have seen everything from a thermocouple taped to the outside of the output end of the tube to probes in the outlet water line, etc etc.

I would think a thermocouple or sensor on the outside of the tube would be a bit of a false test since the outside glass is separated by the water to the inside tube thats the actual laser, in effect only monitoring the temp of the outside of the water jacket. Is it a big variable though?

How about monitoring the outlet of the water passing through, is that a better 1:1 ratio of the temp of the laser tube?