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Could Lasers Divert Lightning From Buildings?

Wednesday, 23. April 2014 - 13:09

The standard advice authorities offer when lightning starts crackling across the sky is for people to take shelter inside buildings. Substantial structures offer protection through lightning rods affixed to the roof, electrical wiring and plumbing that can direct the electricity away from occupants and into the ground.
But what is there to protect the buildings themselves from more than 5 billion Joules of energy in a typical lightning strike, which is enough juice to toast 100,000 bread slices? The problem is no small one—the Empire State Building (above) in New York City gets hit by lightning an average of 25 times a year. And Underwriters Laboratories reports that lightning accounts for more than $1 billion in building damage in the U.S. every year.

Many buildings install lightning protection systems to direct lightning’s energy into the ground, which the Insurance Institute for Business and Home Safety says are highly effective at preventing fires and destructive electrical surges after a strike. Now researchers say there might be a next-generation protective system that prevents lightning from hitting a building at all. Their secret weapon? High-intensity lasers.

They realized that for either the detection or lightning protection system to work, they’d need to overcome a major obstacle to firing high-intensity lasers into the atmosphere—such beams currently lose power after only a few inches because of atmospheric turbulence and water droplets suspended in air.

Their solution was to embed the high-intensity laser in the middle of a beam of lower intensity they call the dress beam. This creates a virtual filament in which the dress beam feeds power into the high-intensity center, helping it stay focused and overcome objects that would otherwise cause it to scatter. "Think of two airplanes flying together, a small fighter jet accompanied by a large tanker," said Maik Scheller, a University of Arizona assistant research professor of optical sciences, in a statement. “Just like the large plane refuels the fighter jet in flight and greatly extends its range, our primary, high-intensity laser pulse is accompanied by a second laser pulse -- the dress beam -- which provides a constant energy supply to compensate for the energy loss of the primary laser beam as it travels farther from its source.”

Their work, which was recently published in the journal Nature Photonics, extended the high-intensity laser’s range from 10 inches to seven feet in the lab. Using models to scale up their innovation, they believe they could extend it to 165 feet in real-world conditions.

(The top image shows the case of the intense central beam alone. The beam is focused and a short filament results and the plasma channel dissipates rapidly. In the bottom figure, the beam is accompanied by the dress beam. The filament and the plasma channel is extended manifold. Courtesy University of Arizona.)
Top Gif: ”I caught three direct strikes to the Empire State Building lightning rod after midnight on 4/13/11 during a severe thunderstorm,” wrote YouTube user ESBisMyMuse on the description accompanying this video. “I actually saw a fourth direct hit, but sadly wasn’t filming at the time. I’ve never seen so many hits on the ESB in one night.”

Michael Keller

Source: 
www.genewsroom.com
Tags: 
laser
lightning
optics
Science
tech
weather