primarily for CWA detection, Fountain said, it was perfectly suited for explosives.
“If you understand the principles behind how that system operates, it’s no differ- ent than the ones that are in airports or the ones that they were fielding for explo- sives,” Fountain said. And it’s no different from what JCAD is capable of.
When he returned from Iraq, Fountain started an Army technology objective (ATO) program to see if ECBC could upgrade JCAD to detect explosives. Te widespread misapprehension within DOD that the chemical threat and the explosive threat were separate domains, requiring separate detectors, arose largely from concepts of operation that were written according to individual threats, ignoring others.
As Fountain sees it, CWAs and explosives are both chemicals, so one device should be able to detect both. Te premise is simple: It’s a better idea to give Soldiers a single piece of equipment that can do several different things well rather than several pieces of equipment, each of which can do only one thing.
ION-MOBILITY SPECTROMETRY 101 To understand how the JCAD works and why it’s useful in detecting chemical agents and explosives, it helps to under- stand what ion-mobility spectrometry is and does. Ions are either positively or negatively charged atoms or molecules. A neutral particle (neither positively nor negatively charged) can be ionized by exposing it to an electrical field.
Tat’s what JCAD does. It has a pump, Fountain said, that draws in ambient air. Te air passes over an element that gives the molecules in the air a charge, ionizing them. Molecules of different chemicals each have a different
FIRST OF A KIND
JCAD has been modified from its original design, right, for detecting chemical warfare agents into a dual-use item that can also detect explosives, making it the Army’s first portable, near-real-time explosives detector. (Photo courtesy of U.S. Army ECBC Public Affairs)
weight and mass, and those unique properties make it possible to determine what kinds of chemicals may be present in an air sample.
shape,
On the opposite end of the JCAD cham- ber from the intake is a detector, an electrical grid that attracts the particles. Te particles travel at a rate of speed pro- portionate to their shape and size (hence ion mobility). Generally, Fountain said, smaller molecules arrive quickly while larger molecules travel more slowly. Ion- mobility spectrometry tells you the mass of a molecule by measuring its size and weight, then combining that with its speed through the chamber toward the detector. “It’s a simple but elegant way of measuring the mass of an ion,” Fountain said. When you know the mass of the ion, and you know its charge—which JCAD does because it charged the mol- ecule—then you can calculate the ratio of mass to charge.
Tat calculation tells you what kind of chemical the molecule is—and whether it’s a hazard. “You’re really just imparting a charge, attracting it to a pole,” Foun- tain said, “and then counting how long it takes to get there—it’s generally micro- seconds.” Te software in the JCAD does all of these calculations very rapidly.
ONLY ONE SYSTEM NEEDED Given that there were already tens of thousands of JCADs fielded, the next logical step for Fountain was to have the JCAD work to its full potential. “In my mind, it made a lot more sense just to have one system that was already fielded that we had the logistics to support [and] we had the training programs already in place to train Soldiers in how to use it,” he said. “It didn’t make sense that we would buy commercial off-the-shelf that was really designed for airport screening and put it in a military environment and not have it perform as well.”
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