Homeland Security

Tuning Out the Background

November 1, 2005 By: Melanie Martella, Sensors Sensors

Tracking down radioactivity is easy, right? You just turn on a Geiger counter and swoosh it around until you hear rapid clicking. Well, no. While you can spot radioactivity that way you can't necessarily distinguish between the natural radioactivity from, say, a nearby granite building or a dirty bomb some distance away. In fact, emergency responders frequently deactivate their radiation detectors because of repeated false alarms. Now the responders have a new weapon in their arsenal. Mine Safety Appliances Co. (www.msanet.com) is using RFTrax CZT radiation sensors in its SAFESITE wireless system to detect dirty bombs (among SAFESITE's other homeland security and emergency response applications).

CZT (Cadmium Zinc Telluride) radiation detectors have been used for years in medical and laboratory instrumentation. RFTrax's CZT sensors are about the size of a disposable lighter and can run for years on small batteries. They offer a broad dynamic-detection range and are sensitive to low radiation levels—this capability lets users adjust the sensitivity of the sensor, decreasing the number of false alarms. According to Hal Haygood, president of RFTrax, "Traditional gamma detection technologies have very limited dynamic range. They fail to distinguish between low levels of nonharmful radiation and releases of higher and harmful radiation."

Contact Bob Goertz, RFTrax, Sugar Land, TX, 281-276-5907,

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