Extending life of plasma channels could allow lasers to be used as lightning rods
Today's simple metal lightning rods may be on their way to obsolescence. That's because scientists at The Hebrew University of Jerusalem are developing a high-tech alternative that could potentially reach higher and be more effective – laser lightning rods.
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When a high-power laser is shot into the sky, it ionizes airborne molecules in the process. As a result, even once the laser itself is shut off, a trail of ionized particles known as a plasma channel is left in its place. Plasma channels conduct electricity, not unlike a good ol' steel rod.
Led by scientist Jenya Papeer, the Jerusalem team successfully created plasma channels measuring 100 microns in diameter, by firing a laser in pulses lasting just 100 femtoseconds each. Unfortunately, however, after three nanoseconds the plasma cooled off and the channels ceased to exist.
In order to boost those trails' longevity by a factor of 10, the researchers added a second laser that is fired in 10-nanosecond bursts along the path of the first one. Its wider beam envelopes the plasma created by the first beam, keeping it hot and conductive. By boosting the power of that second laser, or even by adding additional beams, it is hoped that the lifespan and the length of the plasma channels could be lengthened further.
Speaking of which, though, the first plasma channels to be produced were only a meter (3.3 ft) long. The researchers addressed this limitation by creating an array of lenses that change the way in which the laser is focused. As a result, it now creates a series of three one-meter-long channels linked end-to-end, effectively forming one 3-meter plasma channel.
That said, by further adjusting the focus and using a powerful enough laser, it should be possible to produce any number of linked plasma channels, creating a lightning rod of any desired length.
A paper on the research will be presented on Oct. 22nd at the Frontiers in Optics conference, in San Jose, California.
Source: The Optical Society