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Inspired mine detection

A Lancaster father and daughter break ground in simpler, cheaper land-mine sensors, using radar and sound waves.

Tim Bechtel plants a model mine in a sand box for a demonstration how his system can locate the device. (  DAVID SWANSON / Staff Photographer )
Tim Bechtel plants a model mine in a sand box for a demonstration how his system can locate the device. ( DAVID SWANSON / Staff Photographer )Read more

Buried in a harmless-looking sand pit in Lancaster were a bunch of plastic devices designed with gruesome intent: to kill or maim anyone who steps on top of them.

They were land mines - in this case, filled with inert materials instead of explosives, but otherwise no different from millions of devices buried in war-torn regions around the world.

Yet Tim Bechtel could see them. He moved a cylinder-shaped device back and forth over the sand, emitting a steady stream of radio waves - radar - and bit by bit an image of the mines emerged on a nearby computer screen.

Bechtel, a geophysicist who teaches at Franklin and Marshall College and the University of Pennsylvania, is part of an international group developing the handheld detector. The team's goal is to provide better tools for humanitarian de-mining organizations, who work in regions that remain dangerous long after soldiers have stopped fighting.

So far the radar prototype seems to do the trick, detecting even the common plastic mines that elude metal detectors.

It is a few years away from being field-ready, and it does not work well in wet soil. But for a solution to that problem, Bechtel need look no farther than his own house in Lancaster.

His 17-year-old daughter, Marian, has invented a different device that detects land mines with sound waves. As a result, she was a finalist this year in the Intel Science Talent Search, a prestigious national competition for high school seniors.

That may seem like a tender age to be tackling the issue. But Marian - a math and science whiz who took calculus in ninth grade and is graduating a year early in June - was even younger when she had her first flash of insight on land mines. She was in junior high.

Her father's research partners, who hail from Russia, Italy, England, and Japan, stopped being surprised by the teenager long ago.

"She has done very good work," said team member Lorenzo Capineri, a professor of electronics at the University of Florence. "She has quite a mature approach."

The teenager also has a personal motivation.

Years ago, her cousins lived in a part of Mozambique that was still recovering from civil war. They told Marian that on family car trips in the African nation, they did not dare leave the road if they had to go to the bathroom. The reason?

They were afraid they'd step on a mine.

Science for peace

Estimates vary on how many mines are in the ground around the world, but it is generally agreed that the number is in the many millions. Mines are prevalent in 72 nations, according to Landmine and Cluster Munition Monitor, an international group that tracks the issue.

In 2010, mines and "explosive remnants of war" killed or maimed at least 4,000 people, the group says - though data from some strife-ridden countries are unavailable.

Bechtel got involved with the issue more than a decade ago at the request of Sergey Ivashov, a scientist who had worked for the military in the former Soviet Union.

Ivashov had obtained funds from an international group that sought to encourage peacetime research by researchers like him. He enlisted Bechtel because the Pennsylvania scientist had experience in locating unexploded ordnance on U.S. military bases, using metal detectors. Partners with other expertise joined from Italy, Japan, and England.

The group has remained together ever since, developing a radar-based detector and scraping together extra funds as they go.

Various nonprofit groups and the United Nations are engaged in de-mining programs, but new mines are placed faster than old ones are removed. Metal detectors are useless against mines that contain no metal, so workers typically must probe the ground manually, with spikes. Advancing an inch at a time, they insert the spikes diagonally into the earth so as not to hit a mine's trigger mechanism, typically located on top.

The U.S. military uses devices that emit radar and also contain a metal detector, but they cost tens of thousands of dollars and cannot distinguish between all-plastic mines and other debris, Bechtel said.

The device Bechtel and his partners are working on offers an advantage: It reveals an image of what's underground. And the group estimates it can make the device for less than $5,000.

Other refinements remain before the mine detector is field-ready. The team is working to make the images sharper, and is also developing neural-network software to better distinguish mines from rocks and trash. In Italy, Capineri is developing a robot to operate the device.

Then there's the fact that radar doesn't work in wet soil.

Enter the teenager.

From music to mines

Marian Bechtel was playing the piano one day - she thinks it was in eighth grade, while her father is sure it was seventh - when she noticed something happening with her father's banjo, hanging on a wall nearby.

"I noticed when I played certain notes, the strings on the banjo would resonate," said Marian, who also plays trumpet and violin.

She was already surrounded by talk of land mines. Her older sister, Ellen, now a geology major at Wellesley College, had helped her father in the research. And Marian had heard the team discussing the wet-soil problem. So she figured, why not try sound waves?

Tim Bechtel did not know much about the topic, so he urged his daughter to ask for guidance from his Italian colleague Capineri, who had previously studied an acoustic approach.

Marian became consumed by the project, reading papers and spending hours in the basement testing various ideas. She built prototypes and entered them in science fairs for several years, and last month she demonstrated the latest model at a White House science fair.

Marian was in Washington again last week, with the rest of the 40 finalists in the Intel competition. She didn't win, but her peers chose her to receive the Seaborg Award, given to the finalist who best represents a commitment to scientific cooperation and communication.

Her device works like this. First, the operator turns on a concrete vibrator - a device normally used to release trapped air from freshly poured concrete. The vibrator causes nearby buried objects to resonate, somewhat like the strings on Tim Bechtel's banjo.

The actual mine detector consists of two sensitive microphones, wired in such a way that background noise is canceled out - enabling the operator to detect the faint sound waves emanating from the buried objects.

As both the radar and acoustic approaches have their advantages, perhaps someday versions of both might be used in the field, Tim Bechtel said.

For now, he thinks it's impressive enough that a teenager could contribute.

"She's an anomaly," he said. "I don't understand her sometimes. Where the ideas come from, they just seem to spring out of her."

A father-daughter team has helped develop ways of detecting buried land mines. Watch their devices in action at

www.philly.com/mines EndText