Metal detector could one day tell whether buried objects are unexploded bombs or just harmless junk.
The world is riddled with unexploded
bombs left behind following munitions tests and warfare. Governments
want to dig them up so the land they are in can be used again. The
problem is, "it's difficult to distinguish the unexploded bombs from
man-made clutter or junk", says Eugene Lavely of BAE Systems in Burlington, Massachusetts.
Lavely and his colleagues have
developed a technique, called time-domain electromagnetic induction, to
tell risks from rubbish. Like "a fancy metal detector", it uses a coil
to send an electromagnetic pulse 15 metres into the ground, Lavely
reported at the American Physical Society meeting in Boston last week.
The pulse makes the things it hits reverberate like a struck drum, and
the team have identified the reverberation signal of a torpedo-shaped
metal object with a hollow core - where explosives may lie.
The researchers are now refining the
method so that it is accurate enough to meet US standards, which require
99.9 per cent confidence that all bombs have been dug up before land
can be used.
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