It will not take long for the Muzzies in Iraq to figure this one out.
This millimeter beam weapon sounds like a typical military-industrial response, too expensive and delicate, but lots of CASH for them that make it.
A better idea, at least for crowd control in a riot : put some slickery stuff like aqua gel in the water cannon spray. You take FRICTION, as in foot TRACTION, for granted; ever slipped and fell on ICE? So with the street surface suddenly like ice/grease, a mob of rioters becomes a writhing mass of WORMS, squirming and cursing, but going nowhere...a better, non-lethal solution than zapper-beams.