Lightning causes up to 24,000 fatalities a year globally in addition to extensive harm, creating forest fires, power outages, and damaged infrastructure. The Benjamin Franklin lightning rod is still the finest method of defence today. However, these rods don’t always provide the best security for delicate areas.
The Laser Lightning Rod, or LLR, has been created by a European partnership made up of the University of Geneva (UNIGE), École Polytechnique (Paris), EPFL, hes-so, and TRUMPF scientific lasers (Munich). The LLR was put to the test on Säntis’ peak (in Switzerland), and the researchers now have evidence of its viability. Even in bad weather, the rod may divert lightning across a few dozen metres. The journal Nature Photonics has published the study’s findings.
One of nature’s most intense occurrences is lightning. Lightning is a sudden electrical discharge that may occur inside a single cloud, between many clouds, between a cloud and the earth, or vice versa. It can produce millions of volts and hundreds of thousands of amps. Lightning is both interesting and deadly, causing up to 24,000 fatalities annually. It also causes massive destruction of several billion dollars, including power outages, forest fires, and destroyed infrastructure.
Since Benjamin Franklin created the lightning rod in 1752—a pointed, conducting pole made of metal attached to the ground—lightning-protection tools have hardly altered. The conventional rod is still the best exterior defence since it covers a surface with a radius that is about equal to its height.
Therefore, a 10 m-high rod will effectively secure a 10 m-radius region. The technique is not ideal for securing critical locations across a large region, such as an airport, wind farm, or nuclear power plant, since the height of the masts cannot be endlessly increased.
creating conductive air
In close collaboration with EPFL (EMC Lab, Prof. Farhad Rachidi), TRUMPF scientific lasers, ArianeGroup, AMC (Prof. A. Mysyrowicz), and the School of Engineering and Management, a European group headed by UNIGE and École Polytechnique (Paris) has been examining ways to overcome this challenge (hes-so, Prof. Marcos Rubinstein).
It has been developing a gadget called the Laser Lightning Rod (LLR). The LLR was employed as a lightning guide, producing channels of ionised air along its beam. It might practically extend its height as well as the surface of the region it is protecting by rising above a conventional lightning rod.
According to Jean-Pierre Wolf, full professor in the Department of Applied Physics at the Physics Section of UNIGE’s Faculty of Science and the study’s final author, “When extremely high power laser pulses are released into the atmosphere, filaments of highly intense light develop within the beam.” Professor Wolf says, “These filaments ionise the nitrogen and oxygen molecules in the air, releasing electrons that are free to travel. “This plasma, or ionised air, turns into a conductor for electricity.”
tests at 2,500 metres of height
The LLR project required the creation of a brand-new laser with an average power of one kilowatt, a pulse energy of one joule, and a pulse length of one picosecond. The rod was created by TRUMPF scientific lasers and is 8 metres in length, 1.5 metres in width, and weighs more than 3 tonnes. On the Säntis peak (in Appenzell, at a height of 2,502 m), which was previously outfitted by EPFL and HEIG-VD / HES-SO to study lightning, this terawatt laser was tested.
It was concentrated atop a Swisscom telecommunications company’s 124 m transmission tower, which had a conventional lightning rod installed. This is one of the buildings in Europe that is most often struck by lightning. “The biggest challenge was that the advertising was life-size. We had to set up a space where we could instal and safeguard the laser “According to Pierre Walch, a Ph.D. candidate at the Laboratoire d’Optique Appliquée (LOA), a collaboration between the French research institutions CNRS, École Polytechnique, ENSTA Paris, and Institut Polytechnique de Paris in Palaiseau.
Every time a storm was expected between June and September 2021, the laser was turned on. It was necessary to shut the region in advance to aviation travel. The project’s organiser, Aurélien Houard, a research scientist at the Laboratoire d’Optique Appliquée (LOA), notes that the goal was to determine if there was a difference with or without the laser. We contrasted the data gathered when the tower was naturally hit by lightning and when a laser filament was created above it.
even when there is cloud
The enormous quantity of data gathered required nearly a year to examine. This research now demonstrates that the LLR laser can successfully direct lightning. Further explaining, Professor Wolf says, “From the first lightning incident employing the laser, we observed that the discharge could follow the beam for about 60 metres before reaching the tower, indicating that it expanded the radius of the protective area from 120 m to 180 m.”
The data analysis also shows that the LLR, unlike other lasers, operates even in adverse weather, such as fog, which may halt the beam and is often present at Säntis’ peak. This is because the LLR physically pierces the clouds. Only in the lab has this result ever been seen before. The consortium’s next move will be to progressively raise the height at which the laser acts. The long-term goal is utilising the LLR to add 500 m to a 10 m lightning rod.
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