On what kind of machine you're going to place the tube?
Mach3 is bad when it comes to control laser. I can suggest you to use GRBL (on Arduino platform) as motion controller when dealing with lasers.
On machine that I use I have a router () and 2.5W laser module. Routing-cutting-engraving is controlled with Mach3, when it comes to laser, I just swap BOB with GRBL and use different software (LaserGRBL) or LightBurn.
LaserGRBL:
Mach3: