My first HeNe laser - WOO HOO!!!

[diachi]

Three phases. That's 208 x 45 per phase.

So that means you're losing about 20kW of power in the PSU? They aren't THAT inefficient. The tube is only going to use 7 - 10 kW.

Not quite, you will need to be able to dissipate ~10kW from the water at high pressure and fast flow rates.

That's ~10kW for the tube AND PSU. Some parts of the PSU are also water cooled, i.e. the passbank. So it can't be consuming 28kW, putting out 10W of light and still only producing ~10kW of heat. A magic 18kW of power would need to be disappearing through some hole in space and time!