Cooling a laser tube with room-temperature water is generally considered the minimum. Once the coolant warms up when doing long or high-power job the laser tube starts to destroy itself. To prolong the lifespan of your tube it should really be cooled with chilled automotive coolant. Off-the-shelf chillers start at about AUD$600, however I discovered that my office was throwing out a stack of chiller units that were used in prototyping liquid cooled electric car charging cables. I filled the boot of my Corolla

Two Aspen chiller units joined in series.

Once I got them home and started poking around. I found the compressor is driven by a 24V 3-phase signal. I happened to have a beefy 3-phase brushless motor driver (ESC) leftover from a UAV project a decade ago:

Slightly concerned they couldn't spell “red”.

I measured around 0.340Ω on the windings of the compressor versus 0.170Ω on the chunky brushless motor paired with the ESC. Vaguely in the same ballpark. The specs on the Aspen chiller said the PSU draws 10A at 24VDC, however the ESC could happily supply 100A. This will kill the compressor.

Worth the risk!

I hooked up the compressor to one of the ESCs and attached a UAV signal receiver to it. I gradually increased the “throttle” and the compressor started whirring! The cold side got cold and the hot side got hot! A miracle!