World travelers know that "getting there" is not always glamorous. They have stories of missed flights, jet-lagged meetings and worse. But now they can feel a little safer because of a device about the size of a pager. A relatively new cause of concern for government officials, airport personnel, border police and customs officers is the smuggling or illegal transport of nuclear materials. In an effort to help stop the movement of these materials, Santa Barbara Sensor Technologies of Santa Barbara, Calif., developed the Radiation Pager. The device is a self-contained gamma-ray radiation detector hundreds of times more sensitive than Geiger-Muller tube detectors of similar size. It can also withstand the rough-and-tumble daily scramble of police duty.What makes this detector unique is its new miniature photomultiplier tube (PMT) from Hamamatsu Corp., used in combination with a cesium iodide scintillator. "Hamamatsu is the only company that had the technology to provide a PMT small enough to fit in the pager-size device," said Kenneth Vadnais, Santa Barbara Sensor's co-founder. "Because of Hamamatsu's PMT we can provide an instrument with increased sensitivity in a compact, rugged, easy-to-use package."The Radiation Pager can be clipped to a belt or carried in a pocket. When x-rays or gamma rays are detected at levels significantly higher than normal, the unit alerts the operator within 1 s by flashing a high-intensity light and either sounding an alarm or vibrating. A single-digit LED and/or audio tone will localize the source of the alarm.The power supply is a proprietary electronic system, and with two AA batteries the device will function continuously for more than a year.Now, when you see a little black box clipped to the belt of a law-enforcement officer, it just might be for something more than calling the station.