That custom case for the laser power supply looks great! Did you make it yourself? If not, where did you get it?
That air assist pump looks pretty slick. How loud is it?
If you arrange your liquid cooling circuit to flow: Header/Expansion Tank -> Pump -> Radiator -> CO2 Tube -> Flow sensor -> Filter ->
You will gain the following benefits:
Lower Coolant Temperatures in the CO2 Tube (with the radiator right before the CO2 Tube, the tube gets the coldest coolant. With your current setup your dumping the heat from the pump into the laser tube, depending on the heat dump from your pump this could be negligible)
Increased pump life (pumps tend to last longer when their intake is unimpeded, depending on how restrictive your filter is this could be negligible)
Faster error response time (if the tube was to clog or break, the sensor would know immediately. with your current setup, most of the coolant in the circuit would have to empty before the flow sensor values would go out of range)
You mentioned that because the PC liquid cooling radiator is made from brass that it will cause conductive contamination; are you referring to galvanic corrosion? What metals are you mixing in your loop? For reference, I ran a liquid cooled workstation 24/7 for an entire year at approx 35C which contained brass, copper, nickel, silver, delrin, acrylic, and premixed liquid coolant with no adverse affects.
In any case, it’s common practice to drain, flush, and refill liquid cooling loops once a year; which is how often I drain my loops. It’s not ideal to simply top off the loop when using coolant containing additives; the reason being, when evaporation occurs, some of the additives will be left behind and when you top off the coolant it becomes unbalanced and those additives can build up and restrict flow. This is an issue for CPU coolers which often contain small pin matrixes but shouldn’t be a major concern in our application.