Can Lasers Shoot Lightning Out of the Sky?

30 September, 2015

Researchers from the Hebrew University in Jerusalem have developed new methods to make longer streams of plasma with greater longevity, that could lead to laser-powered lightning rods

Researchers from the Hebrew University in Jerusalem have developed new methods to make longer streams of plasma with greater longevity, that could lead to laser-powered lightning rods

LASER

A team of researchers from the High Intensity Laser Lab in The Hebrew University of Jerusalem, Israel, have demonstrated new techniques that bring lasers as lighting rods closer to reality.

When a powerful laser beam shoots through the air, it ionizes the molecules, leaving a thin trail of hot, ionized particles. Because this stream of plasma conducts electricity, it could be used to channel away a potentially damaging lightning bolt. The researchers found ways to make the length of the plasma channel more than 10 times longer relative to present methods.

Dr. Jenya Papeer from the lab, will present the work at Frontiers in Optics, The Optical Society’s annual meeting and conference in San Jose, California, USA, on 22 October 2015. The researchers created a channel of plasma by firing a powerful laser that produces a pulse lasting a fleeting 100 femtoseconds (one femtosecond is 10-15 seconds).

The problem is that the resulting plasma stream, 100 microns in diameter, lasts for only about three nanoseconds. After that time, the plasma cools off, the electrons recombine with the atoms and the channel disappears.

To extend the lifetime of the plasma channel, the researchers shot another laser whose beam overlaps the plasma. The secondary laser, which produces 10-nanosecond bursts, keeps the plasma hot and prevents the electrons from recombining so quickly, extending the longevity of the plasma channel by more than a factor of 10.

The team is now working on ways to fire a more powerful secondary laser — or maybe additional beams — to increase the lifetime of the channel even more. In principle, Papeer says, a longer life could also extend the length of the plasma channel, which stretches for only about a meter.

The laser creates the trailing plasma stream analogous to the way a pen leaves behind a line of ink. If the ink disappears soon after the pen makes a mark, you can only ever draw a short line. But if the ink were to last longer, you could draw a longer line. Likewise, a longer-lasting plasma would result in a longer channel.

Control the Lighting with Light

The researchers also devised a method to lengthen the plasma channel. The laser beam typically generates multiple plasma channels that spread out randomly along the laser beam. But by designing an apparatus of lenses that controls how the laser is focused, the researchers were able to make three plasma channels that line up in sequence, one after another.

The result is a three-segmented plasma channel that acts as a single, three-meter long channel. “The beauty is that you can extend it for pretty much as long as you want, as long as you have the proper optical set up and a laser beam with enough power,” Papeer says. In fact, this ability to extend the channel to an arbitrary length is the main advantage of this method.

The next step, Papeer says, is to combine both methods to produce a plasma channel that’s greater in both lifetime and in length. Maybe sometime in the future this new method will be able to replace the familiar metal poles of lightning rod, that was invented 250 years ago by Benjamin Franklin.

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Posted in: ElectroOptics , Featured Stories , News

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