To be placed as needed along the Mexican / U.S. border, as a more cost effective alternative than a fence.
The weapon - mounted atop a Humvee - reportedly has a range of 500 metres within which it heats its targets' skin to 50°C. According to the BBC, journalists who voluntarily put themselves in the firing line during a demonstration at an air base in Georgia, "described the sensation as similar to a blast from a very hot oven - too painful to bear and forcing them to dive for cover"
http://www.raytheon.com/products/silent_guardian/
The system's antenna emits a focused beam of millimeter waves, around 95 GHz. in frequency, for wetback roasting, or controlling the infestation from the Mexican border, as it's called
The beam travels at the speed of light and penetrates the skin to a depth of 1/64 of an inch, producing an intolerable heating sensation that causes the targeted illegals to instinctively flee or take cover. The sensation ceases immediately when an illegal moves out of the beam or the operator steers the beam away.