Everything at a Stop

T-Rays
The ThruVision T4400 T-ray detector sees a gun hidden under clothing.Terahertz radiation, or T-rays, occur at a frequency of around a trillion hertz—between microwaves and infrared on the electromagnetic spectrum. Unlike X-rays, T-rays are nonionizing, so they don’t carry a cancer risk. They can penetrate clothing, packaging and a few millimeters into the human body, making them ideal for security screening and medical applications such as skin-cancer and tooth-cavity detection. Until now, they’ve been difficult to generate, but Harvard researchers recently filed for a patent on the first room-temperature source of coherent T-rays, and scientists at Argonne National Laboratory are developing a portable T-ray generator. Lower-resolution passive detection systems that pick up natural T-ray emissions are already on the market: The Wayne County Sheriff’s Office, in Detroit, is testing a scanner built by British company ThruVision to screen anyone entering its criminal courts.